BEIRUT (Reuters) - Syria’s army and its allies on Saturday reached the edge of al-Sukhna, the last town held by Islamic State in Homs province and a key step in their multi-pronged offensive against the militants, a Hezbollah-run military media unit said.

Sukhna is on the main desert highway between Palmyra and the government’s besieged enclave at Deir al-Zor, about 130km (80 miles) to the east.

The Hezbollah media unit earlier said the Sukhna gas field and heights above the town were within range of the army and its allies’ fire.

A war monitor, the Britain-based Syrian Observatory for Human Rights, reported that the army had similar fire control across the whole town and that most Islamic State militants there had fled.

The army and allies including Lebanon’s Hezbollah and other Shi’ite militias are pushing through Syria’s eastern desert to assault Islamic State’s heartland along the Euphrates valley.

Another prong in the offensive is being waged further north, where the army and its allies are advancing along the southern bank of the Euphrates south of Raqqa. Russian jets are supporting the campaign.

U.S.-backed Kurdish-led forces have taken swathes of the land north of the Euphrates and are pushing into Raqqa, previously the jihadists’ Syrian capital.