The "Islamic State" abducted more than 300 workers from a cement factory in Dumier, Syrian state media reported on Thursday, as government troops pushed into the key IS-held territory.

A manager from the al-Badia Cement Factory in Dumeir said all contact with the men had been lost.

"The company informed the ministry that it has not been able so far to communicate with any of the abductees," the state news agency SANA quoted the man as saying.

Dumeir was the site of a surprise IS-launched attack against government forces earlier in the week.

Key supply route cut off

The kidnapping comes amid separate gains by both government forces and Western-aligned rebels in the fight against "IS." In late March, the army of President Bashar al-Assad recaptured the historic city of Palmyra, a UNESCO world heritage site. The embattled leader called the victory an "important achievement."

On Thursday, observers and activists said that Syrian rebels and their allies had cut off a key supply route along the border between Syria and Turkey.

Factions of the Free Syrian Army reportedly entered the IS-held town of al-Rai, which not only sits along the supply line to Turkey but also to Aleppo.

Peace talks set for April

Meanwhile, leaders from the international community are still aiming for a political end to the war, which has dragged on for five years.

UN Syria envoy Staffan di Mistura announced that peace talks would restart on April 13, after initially suggesting they would begin on April 11.

Di Mistura is meeting with leaders in the region as well as beyond in order to drum up support for the new talks. Among the cities he's set to visit are Damascus and Tehran. He was previously in Moscow, where he met with Russian Foreign Minister Sergei Lavrov.