The Syrian army has sent reinforcements to Palmyra, where ISIL fighters have advanced in some of the heaviest battles in the area since the armed group lost the ancient city eight months ago, according to a military statement.
The Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group had launched an offensive in recent days close to the town, which is on UNESCO's world heritage list.
They have since taken over areas to the northwest and southeast of Palmyra, and have reached the edge of the city. Clashes continued on Saturday, the army added in its statement.
A rebel commander from the Jaish al-Mujahideen group based in the Aleppo countryside said the ISIL attack was forcing the Syrian government to divert troops from Aleppo, Reuters news agency reported.
The Syrian army and its allies are currently on the verge of a major victory against rebel groups in Aleppo.
WATCH: Recapturing Palmyra - The story and the spin
According to the Syrian Observatory for Human Rights, a UK-based group, fierce fighting is continuing on the ground near Palmyra, while at the same time the Syrian air force has launched air strikes against ISIL fighters.
"The noise of fighting can be heard inside the town," said Rami Abdul Rahman, the director of the Observatory, whose organisation relies on civilian and military sources across Syria.
Since Thursday, ISIL fighters had been only four kilometres from the town, according to Abdul Rahman.
The Observatory said at least 49 pro-government force members have been killed by ISIL since Thursday in the offensive in the province of Homs, where Palmyra, known as Tadmur in Arabic, is situated.
ISIL seized control of several towns in the province, including Palmyra, in May last year, and damaged its ancient sites extensively.
The Syrian government controls most of Homs province, but its troops are regularly attacked by ISIL fighters, notably when they are in isolated areas, including in oil fields, which are difficult to protect.
Source: News agencies