Syrian army has taken full control of the strategic town of Qusair, state TV and the rebels say.
Qusair, near the Lebanese border, has been the centre of fighting for more than two weeks between rebels and Syrian troops backed by fighters from the Lebanese militant group Hezbollah.
Syrian state TV said a large number of rebels had died and many had surrendered.
The rebels said they withdrew overnight in the face of a massive assault.
Earlier, the military leader of the main rebel umbrella group, the Free Syrian Army, said his fighters were prepared to take the conflict inside Lebanon in pursuit of Hezbollah fighters.
General Selim Idriss of the Free Syrian Army (FSA) – the main umbrella rebel group – said Hezbollah fighters were “invading” Syria and Lebanon was doing nothing to stop them.
Qusair lies just 6 miles from the Lebanese border and along major supply routes.
Syrian pro-government forces, including Hezbollah fighters, have been battling rebels for control of the town for more than two weeks.
But on Wednesday, Syria’s Sana state news agency said the “heroic armed forces have returned security and stability to all of the town”.
Sana said a large number of “terrorists”, as the state refers to the rebels, had been killed and many had surrendered. It said the army was now destroying barricades and weapons caches and searching the town for explosives.
The army said the victory was “a clear message to all those who share in the aggression on Syria … that we will continue our string of victories until we regain every inch of Syrian land”.
“We will not hesitate to crush with an iron fist those who attack us. … Their fate is surrender or death,” it said.
In Lebanon, Hezbollah’s Al-Manar TV reported “widespread collapse” of the rebel forces in the town, while one Hezbollah fighter told Reuters news agency: “We did a sudden surprise attack in the early hours and entered the town. They escaped.”
Syrian army has taken full control of the strategic town of Qusair
In a statement also quoted by Reuters, the rebels said: “In face of this huge arsenal and lack supplies and the blatant intervention of Hezbollah… tens of fighters stayed behind and ensured the withdrawal of their comrades along with the civilians.”
The British-based Syrian Observatory for Human Rights, an activist group that monitors the conflict, said Hezbollah fighters had “overrun” Qusair after an “intense bombardment cover overnight by regime forces, which continued until dawn today”.
“Reports indicate that the rebel forces retreated from the city due to lack of ammunition and men, this comes despite the many promises that supplies would reach the rebels,” it said on its Facebook page.
It also expressed concern for the more than 1,200 people it said were injured in Qusair, and urged the Red Cross to go in.
Last week, the Red Cross said it was “alarmed” by the worsening humanitarian situation and appealed for immediate aid access. Syrian Foreign Minister Walid al-Moualem reportedly said last week that the agency would be allowed in once military operations were over.
According to new reports, although there are pockets of rebel resistance to the north of Qusair, the government is hailing its recapture as a strategic victory.
The move is also of symbolic importance in the run-up to a proposed peace conference as neither side wants to go into the talks looking weak.
Russia and the US are meeting in Geneva on Wednesday to try to arrange a date and other details of the conference. But it remains unclear whether it will go ahead as the Syrian opposition has neither confirmed it will attend nor established a credible delegation.
More than 80,000 people have been killed in Syria and more than 1.5 million have fled the country since an uprising against Bashar al-Assad began in 2011, according to UN estimates.
The UN reported on Tuesday that the war had reached “new levels of brutality”, with evidence of massacres and children being taken hostage of forced to witness – sometimes participate in – atrocities.
There is also growing evidence that chemical weapons have been deployed in the conflict.
France’s Foreign Minister Laurent Fabius said on Tuesday that samples taken from Syria and tested in France showed the presence of sarin, and that there was “no doubt that it’s the regime and its accomplices” that were responsible.
Laurent Fabius did not specify where the samples had been collected, but French media reported it had been from the northern town of Saraqeb.
The UK also says it has tested samples which give evidence of the use of sarin in Syria.
Both the Syrian government and the rebels have in the past accused each other of using the weapons.
Strategic town of Qusair:
Estimated population of 30,000 people
Up to 10,000 people have fled to neighboring towns and 1,500 people are wounded, the UN says
Some 23 villages and 12 farms west of Qusair are reportedly inhabited by Lebanese Shia
Near the main route from Damascus to port of Tartous, a gateway to the heartland of President Bashar al-Assad’s Alawite sect
Syrian rebels say they have launched a major offensive to capture key airbase at Taftanaz, in the north of the country.
Video posted on the internet showed fighters attacking the Taftanaz base in an attempt to control a strategic zone between Syria’s two biggest cities, Aleppo and Damascus.
The attack comes a day before a crucial opposition meeting in Doha, Qatar.
It also follows the apparent murder of a number of Syrian troops by rebels, which drew international condemnation.
Separately, Israel said three Syrian tanks had entered the demilitarized buffer zone in the Golan Heights to tackle rebel fighters, prompting an Israeli complaint to the UN forces overseeing a truce in the area.
The attack on Taftanaz took place as dawn broke, with five different units of rebel fighters opening fire with multiple rocket launchers, mortars and other weaponry, according to the video.
This appears to be a major operation aimed not just at striking the airport, but at occupying it.
In recent months, the government forces have been making increasing use of air power to strike areas held by the rebels, who lack anti-aircraft weapons to deter the attacks.
Rebel forces are reported to have taken control of the main roads in much of the area south-west of Aleppo.
The video said the rebel groups involved included several brigades of the Free Syrian Army, but also the radical Islamist al-Nusra Front.
Syrian rebels say they have launched a major offensive to capture key airbase at Taftanaz
Although nothing certain has been established, al-Nusra has been named in connection with the killing of captured army soldiers two days ago at Saraqeb, just 15 km (10 miles) from where this latest attack is taking place.
The UN has said the video that appears to show the murder of the soldiers or pro-government militiamen could be evidence of a war crime.
The footage shows gunmen beating and shooting a group of prisoners who were cowering on the floor.
On Friday, the US said it “condemned human rights violations by any party in Syria”.
State department spokeswoman Victoria Nuland said: “There is no justification for that kind of behavior ever. Anyone committing atrocities should be held to account.”
The question of apparent brutality by some rebel units has become a serious concern ahead of the major opposition meeting being held in Qatar this weekend.
The US is hoping a new leadership will help unify the disparate opposition elements and bring a successful conclusion to an uprising that has killed more than 36,000 people since protests against President Bashar al-Assad erupted in March 2011.
Divisions have arisen not just between Islamist and secularist groups, but also between those operating inside Syria and opposition figures working abroad.
Victoria Nuland said there was a need for cohesion of rebel forces within Syria and a strong organization outside the country that could work with the international community.
A previous opposition meeting in Cairo in July accepted that the Assad government must fall but failed to appoint a committee to act for the opposition internationally.
The US this week signaled the opposition needed to be expanded from the main overseas grouping, the Syrian National Council, to take in more of those operating inside Syria.
Representatives at Doha will include various other religious and secular groupings, plus Kurdish figures and dissident members of Bashar al-Assad’s Alawite sect.
President Bashar al-Assad has said Syrian government needs more time to “win the battle” against rebel forces.
In an interview with pro-government al-Dunya TV, Bashar al-Assad also dismissed as “unrealistic” the idea of creating humanitarian buffer zones within Syria.
Opposition activists say the army has launched offensives across the country to regain control of rebel-held areas.
Heavy shelling was reported on Tuesday in the capital, Damascus, Aleppo, and the north-western province of Idlib.
Bashar al-Assad said the Syrian government was “fighting a battle both regionally and internationally”.
“It definitely needs time to bring it to a decisive end. But I can sum it up in one sentence: we’re heading forward,” he told al-Dunya.
“The situation on the ground is better now, but the conclusion is not there yet. That needs some time.”
President Bashar al-Assad has said Syrian government needs more time to "win the battle" against rebel forces
The security forces were “doing a heroic job in every sense”, he added.
“Everyone is worried about their country – that is normal. But [the rebels] will not be able to spread fear, they never will,” he said.
“I say to Syrians: destiny is in your hands, and not in the hands of others.”
The president mocked senior government and military officials who have defected in recent months, saying their departure amounted to a “self-cleansing of the government firstly, and the country generally”.
Responding to rumors about his whereabouts since a July bombing in Damascus killed four senior officials, he revealed that he was being interviewed from the presidential palace in the capital.
Bashar al-Assad also addressed the proposal by Turkish Foreign Minister Ahmet Davutoglu to set up a United Nations-sanctioned “safe zone” inside Syria to shelter refugees and help distribute humanitarian aid.
“Talk of buffer zones firstly is not on the table and secondly it is an unrealistic idea by hostile countries and the enemies of Syria,” he said.
“Do we go back because of the ignorance of some Turkish officials or do we focus on our relationship with the Turkish people, especially those people who have stood by us during the crisis and were not swayed by the media and material propaganda?”
French Foreign Minister Laurent Fabius admitted on Wednesday that creating a buffer zone would be impossible without imposing a no-fly zone deploying ground forces.
“We are thinking about this. It is very complicated. We cannot do it without the agreement of the Turks and other countries,” he told France Inter radio.
“But what we want is for things to move forward, to make Bashar fall as quickly as possible and at the same time find humanitarian solutions.”
The UN refugee agency warned on Tuesday that as many as 200,000 refugees could flee to Turkey to escape fighting in Syria – almost double the number Turkey has said it can take.
The UNHCR said 5,000 refugees were now arriving at the Turkish border every day, compared to about 500 earlier this month. There are already more than 74,000 in Turkey, and 128,000 in other countries.
There are also thought to be more than 1.2 million internally displaced people in Syria, and 2.5 million in need of humanitarian assistance.
Syrian television reports that a bomb has exploded on the third floor of the state TV and radio building in the capital, Damascus.
Three people were reported wounded and the explosion caused some damage but state TV continued broadcasting.
Rebel forces took over several areas of Damascus in recent weeks, but the army has since regained control of the city.
More than 20,000 troops are now aiming to wrest control of the country’s second city, Aleppo, from the rebels.
A bomb has exploded on the third floor of Syrian state TV and radio building in the capital, Damascus
The explosion in Umawiyeen Square in central Damascus had “ripped the floor” but had left the transmission of the three Syrian channels unaffected.
Pro-government TV channel al-Ikhbariya showed pictures of staff looking after an injured colleague. In June, gunmen attacked its offices, south of Damascus, killing seven people, including journalists and security guards.
Information Minister Omran al-Zoabi told Syrian TV that national media had been targeted in the “desperate and cowardly” attack. An investigation was under way to find out who planted the bomb inside the building, he added.
State TV’s buildings have also been attacked in many provincial cities, most recently in Aleppo.
The army has surrounded Aleppo, Syria’s commercial capital, and tanks have tried to push into two key rebel-held areas, Salah al-Din and Saif al-Dawla, which lie on the main road into the city.
A rebel commander was one of nine people killed in Salah al-Din on Monday, according to British-based group the Syrian Observatory for Human Rights.