Two rival Syrian rebel groups in the northern town of Azaz have agreed a ceasefire.
The Islamic State in Iraq and Syria (ISIS), linked to al-Qaeda, seized the town on Wednesday from the larger Western-backed Free Syrian Army (FSA).
Fighting between rebel groups has raised fears of a war within a war.
The clashes come ahead of a deadline, on Saturday, for Syria to provide a list of its chemical weapons facilities as part of a US-Russian deal for the country to destroy its deadly arsenal.
Russia’s Deputy Foreign Minister, Sergei Ryabkov, is currently holding talks in Damascus about the deal.
But the agreement still faces many hurdles – including the differing opinions of the US and Russia.
US Secretary of State John Kerry said a “definitive” UN report had proved that the Syrian government was behind a deadly chemical weapons attack in the Damascus suburbs of Ghouta on August 21.
But Damascus – backed by Moscow – insists that rebel forces carried out the attack.
The West also wants any UN resolution on Syria’s chemical weapons to include the threat of military force in the result of non-compliance – but Russia objects to any mention of this.
Syria’s President Bashar al-Assad, in an interview with Fox News, said it could take about a year to destroy Syria’s chemical stockpiles and could cost about $1 billion.
Under the ceasefire deal in Azaz the two rebel sides have agreed to exchange prisoners and hand back property.
Two rival Syrian rebel groups in the northern town of Azaz have agreed a ceasefire
It is unclear whether the ceasefire will have an impact on clashes between the groups elsewhere in the country.
Analysts say there is more chance that the US and other Western powers may arm the Free Syrian Army if it shows a distinct separation from the Islamists.
The fighting in Azaz began when a wounded rebel – either from ISIS or from an allied group, al-Muhajireen – was taken to a field clinic and, while there, he was filmed as part of a fundraising exercise.
The wounded fighter demanded the film, and called some of his friends to come and help him.
Free Syrian Army (FSA) rebels from a unit called the Northern Storm brigade were guarding the field clinic, and there was a confrontation which ended up with ISIS launching a full attack on the town, pushing out the Northern Storm brigade.
ISIS is reported to have made a number of arrests of activists, journalists and even Sharia court officials during the time it controlled Azaz.
One eyewitness inside the town said no-one was smoking on the streets – tobacco is forbidden according to strict Islamist doctrine.
While the Azaz violence seems to have been the result of a particular set of circumstances rather than a long-planned offensive, our correspondent says there is a record of skirmishes between the Jihadis and FSA brigades for control of the border crossings into Turkey.
Meanwhile, the party of Syria’s Deputy Prime Minister Qadri Jamil insists he was misquoted in Friday’s edition of the UK’s Guardian newspaper.
Qadri Jamil reportedly told the paper that the civil war had reached stalemate, with neither government forces nor the rebels strong enough to win – and that the government would use proposed talks in Geneva to call for a ceasefire.
But the People’s Will Party said the Guardian journalist was ”neither precise nor professional” about what he quoted Qadri Jamil as saying.
Iranian President Hassan Rouhani has said Tehran is ready to help broker peace in Syria, as part of what he called his country’s “constructive engagement” policy with other nations.
In an article in the Washington Post newspaper, Hassan Rouhani wrote: “We must create an atmosphere where peoples of the region can decide their own fates.”
Correspondents say the article is the latest signal that Hassan Rouhani wants to improve Iran’s relationship with the US and other countries that believe Iran is developing nuclear weapons.
Representatives of Israel and Hamas have begun indirect talks on ceasefire deal that ended the recent violence in Gaza.
The negotiations are being led by Egyptian intermediaries in Cairo.
Hamas is expected to press for an end of the Israeli blockade on Gaza, while Israel wants arms smuggling to cease.
At least 158 Palestinians and six Israelis were killed in the eight-day offensive which Israel said it launched to stop rocket-fire from the territory.
Under the terms of the initial ceasefire, agreed on Wednesday, Israel agreed to end all hostilities and targeted killings, while Hamas agreed to stop attacks against Israel and along the Gaza border fence.
The deal also called for the “opening the crossings and facilitating the movement of people and transfer of goods”, with the timing other details to be discussed “after 24 hours” of the ceasefire coming into effect.
Israeli negotiators are reported to be asking for an assurance that the smuggling of weapons under Gaza’s southern border with Egypt will end.
“Israel is proposing this, no doubt,” Hamas deputy political leader Moussa Abu Marzouk told the AFP news agency.
“But at no stage was it part of the understanding for a ceasefire. They proposed it in the media, but not during the talks,” he said.
Meanwhile, Hamas political leader Khaled Meshaal has telephoned the Palestinian Authority President, Mahmoud Abbas, to say the Islamist movement “welcomed” his bid to have Palestine recognized as a “non-member observer state” at the United Nations.
The announcement by Hamas was unexpected. Its leaders have previously dismissed the UN approach as a waste of time.
Mahmoud Abbas has said he will push for a vote on the issue at the UN General Assembly on Thursday. If it is approved – as it expected to be – it will improve the Palestinians’ chances of joining UN agencies and the International Criminal Court (ICC).
Currently, the Palestine Liberation Organization (PLO), the umbrella group which represents most Palestinian factions and conducts negotiations with Israel, only has “permanent observer” status at the UN.
Israel and the US have threatened financial penalties if the Palestinians press ahead with the UN bid, saying the only way to achieve an independent state is through negotiations.
A ceasefire between Israel and the Palestinian Hamas movement has come into effect.
Under the deal, Israel has agreed to end all hostilities and targeted killings, while Hamas will stop attacks against Israel and along the border.
At least 157 people have died since the flare-up of violence began last week.
Both sides continued to fire on each other as the 21:00 ceasefire deadline approached, but no incidents have been reported since.
Earlier, a bomb exploded on a bus in the Israeli city of Tel Aviv, leaving three people needing surgery.
Wednesday also saw at least 13 people die in Gaza.
Israel has agreed to “stop all hostilities on the Gaza Strip, land, sea and air including incursions and targeting of individuals”, the ceasefire deal says.
“All Palestinian factions shall stop all hostilities from the Gaza Strip against Israel, including rocket attacks, and attacks along the border,” it stipulates.
Egyptian Foreign Minister Kamel Amr announced the ceasefire at a news conference in Cairo with US Secretary of State Hillary Clinton, who joined negotiations on Wednesday.
A statement from the office of Israeli Prime Minister Benjamin Netanyahu said he had agreed to a US suggestion “to give a chance to Egypt’s proposal for a ceasefire and so give an opportunity to stabilize the situation and calm it before there will be need to apply greater force”.
For the truce to hold, Hillary Clinton said, “the rocket attacks [from Gaza] must end and a broader calm must return”.
“Now we have to focus on reaching a durable outcome that promotes regional stability and advances the security, dignity and legitimate aspirations of Palestinians and Israelis alike,” she added.
US President Barack Obama praised the Israeli leader for accepting the deal and said he would seek additional funding for the Iron Dome missile defence system, which destroyed dozens of rockets from Gaza in mid-air during the past week.
Barack Obama also thanked Egyptian President Mohammed Mursi for his efforts.
Ties between Hamas and Egypt have strengthened since Mohammed Mursi was elected earlier this year. Hamas was formed as an offshoot of the Muslim Brotherhood, to which Mohammed Mursi belongs.
Also on Wednesday, Palestinian militants fired more rockets at Israel, while Israel renewed its naval artillery bombardment of Gaza.
Israel launched its current offensive a week ago with the killing of Hamas military leader Ahmed Jabari.
The Israeli government says his assassination, and the subsequent offensive, were aimed at ending rocket fire from Gaza.
More than 150 Palestinians and five Israelis have since been killed.
Israeli officials described Wednesday’s bus explosion as a “terrorist attack”. Hamas praised it but has not said it was behind the blast.