Syrian army has entered the ancient town of Palmyra seized by ISIS last year, state TV has said.
According to observers, the government forces have advanced into a hotel district south-west of Palmyra, a UNESCO World Heritage site.
Officials launched an offensive to retake the city earlier this month, backed by Russian air strikes.
Palmyra is situated in a strategically important area between Damascus and the contested eastern city of Deir al-Zour.
ISIS seized the ruins of Palmyra and the adjoining modern town in May 2015. It subsequently destroyed two 2,000-year-old temples, an arch and funerary towers, provoking global outrage.
The jihadist group, which has also demolished several world-renowned pre-Islamic sites in neighboring Iraq, believes that such structures are idolatrous.
UNESCO has condemned the destruction as a war crime.
State media showed warplanes flying overhead, helicopters firing missiles, and soldiers and armored vehicles approaching Palmyra.
According to the Syrian Observatory for Human Rights, the government forces advanced into the hotel district and reached the start of a residential area but were moving slowly because of mines planted by ISIS.
The Syrian troops were also making incursions from the northern part of the city, the AFP reported.
There were unconfirmed reports of casualties on both sides.
The Observatory said civilians began fleeing after ISIS warned them via loudspeakers to leave the city centre as fighting was drawing closer.
The advance comes after the Syrian army and allied militia took control of several hills overlooking the city earlier this week.
Recapturing Palmyra would be a significant victory for the government and Russia, which withdrew most of its forces last week after a six-month air campaign against opponents of President Bashar al-Assad that turned the tide of the five-year civil war in his favor.
Despite the reported setbacks, ISIS claimed its fighters inflicted heavy casualties on the advancing forces, according to its weekly publication Al Naba.
On March 23, ISIS issued pictures purported to show several Syrian army vehicles destroyed by its fire. However, its daily radio news bulletins have not mentioned the fighting in Palmyra in the last few days.
Syrian army has reached the outskirts of the ancient city of Palmyra, after driving back ISIS militants.
According to the UK-based Syrian Observatory for Human Rights, Syrian government troops were now only 1.2 miles south of the UNESCO World Heritage-listed ruins.
ISIS militants seized Palmyra and the adjoining modern town in May 2015.
They subsequently destroyed two 2,000-year-old temples, an arch and funerary towers, drawing global outrage.
ISIS, which has also demolished several world-renowned pre-Islamic sites in neighboring Iraq, believes that such structures are idolatrous.
UNESCO has condemned the destruction as a war crime.
The Syrian Observatory, which relies on a network of sources on the ground in Syria, told the AFP news agency that government forces were on March 23 only 1.2 miles from Palmyra’s southern outskirts and 3 miles from its western edge.
The governor of Homs province, Talal Barazi, confirmed the advance and said troops were now stationed on several hills overlooking the Greco-Roman ruins.
“There is continuous progress by the army from all directions,” he was quoted as saying by the Associated Press.
Talal Barazi added that he expected “positive results” over the next few days.
Syrian government forces launched an offensive to retake Palmyra at the beginning of March, backed by heavy Russian air strikes.
Last week, the Russian military said its aircraft were flying up to 25 sorties a day over Palmyra to help liberate what President Vladimir Putin has described as a “pearl of world civilization”.
Palmyra is also situated in a strategically important area on the road between Damascus and the contested eastern city of Deir al-Zour.
ISIS militants have reportedly captured the Syrian town of Maheen, in central Homs Province, from government forces.
The fighters launched the offensive with two suicide car blasts on October 31, the UK-based Syrian Observatory for Human Rights says.
Clashes were also taking place in nearby Sadad, a mostly-Christian town.
The latest development comes amid air campaigns in Syria by Russia and a US-led coalition.
ISIS has been expanding from its mainly northern and eastern strongholds towards Homs in central Syria in recent months. The group overran the town of Tadmur – home to the ancient ruins of Palmyra – and al-Qaryatain town.
The latest offensive on Maheen and Sadad brings ISIS to within 13 miles of the main road that links the Syrian capital Damascus to Homs and other cities further north.
The Observatory said at least 50 government soldiers were killed or wounded in the fighting. The attack on Maheen began late on October 31 with twin suicide car bombs, a favored tactic for ISIS militants launching an assault.
By November 1 the Observatory reported that the whole town was reported to be in ISIS hands. An ISIS statement also said the group had taken Maheen.
Maheen is home to a large military complex and arms depot.
Meanwhile, clashes between government troops and ISIS are said to be continuing on the outskirts of Sadad. The town is home to Syria’s Assyrian Christian minority, where the ancient language of Aramaic is still spoken.
It comes amid continued Russian air strikes in support of Syrian President Bashar al-Assad, which Russian officials say are targeting ISIS and other “terrorist groups”.
However, activists on the ground say the strikes have been hitting moderate rebels and civilians in western areas, where ISIS have little or no presence.
They said more than 60 people were killed by Syrian army raids and Russian strikes in the northern province of Aleppo on October 31.
On October 30, more than 70 people were reported killed and hundreds more wounded in an air strike and shelling on a market in the rebel-held Damascus suburb of Douma.
In an attempt to ward off the attacks, rebel groups in Douma are reportedly using captured soldiers and other people associated with the government as human shields.
The US-led coalition, which is also hitting ISIS targets in Syria, said on November 1 it had conducted nine air strikes across the country, including in Mar’a and al-Hawl, in the north.
This week the White House announced that fewer than 50 US special forces troops would be sent to Syria to assist anti-government rebels in fighting ISIS.
Separately on November 1, Syrian Foreign Minister Walid Muallem met UN peace envoy Staffan de Mistura in Damascus to discuss ongoing international talks on the Syria conflict.
ISIS militants have executed three captives in Syria’s ancient city of Palmyra by tying them to columns and blowing them up, activists say.
The identities of those reportedly killed on October 25 have yet to be given.
However, they are thought to be the first to have been killed in that way since the jihadist group seized the ruins in May.
ISIS has destroyed two 2,000-year-old temples, an arch and funerary towers at Palmyra, one of the most important cultural centers of the ancient world.
The Islamic State believes that such structures are idolatrous. The UN cultural agency, UNESCO, has condemned the destruction as a war crime.
The Syrian Observatory for Human Rights, a UK-based group that monitors the conflict in Syria, cited local sources in Palmyra as saying that on October 25 ISIS militants tied three detainees to Roman-era columns and then blew up the structures with explosives.
An activist from Palmyra, Khaled al-Homsi, said ISIS had yet to tell locals the identities of the three individuals or say why they had been killed.
“There was no-one there to see [the execution]. The columns were destroyed and IS has prevented anyone from heading to the site,” he told the AFP news agency.
Another activist, Mohammed al-Ayed, said ISIS was “doing this for the media attention”.
After overrunning the ruins of Palmyra and the adjoining modern town, also known as Tadmur, ISIS militants used the ancient theatre for the killing of 25 Syrian soldiers.
They also beheaded archaeologist Khaled al-Asaad, who looked after ruins for 40 years, after he reportedly refused to reveal where artifacts had been hidden.
Earlier this week, ISIS posted images online purportedly showing militants driving a tank over a captured soldier, who it alleged had himself driven over militants.
ISIS has blown up three funerary towers at the ancient city of Palmyra, Syria’s antiquities chief Maamoun Abdul Karim has said.
Maamoun Abdul Karim told the AFP that “the best preserved and most beautiful” had been destroyed.
The multi-storey sandstone monuments, standing outside the city walls in an area known as the Valley of the Tombs, belonged to rich Palmyrene families.
Their demolition comes only days after ISIS blew up Palmyra’s two main temples.
The group, which captured the UNESCO World Heritage site from government forces in May, has previously destroyed two Islamic shrines near Palmyra, which they described as “manifestations of polytheism”.