A Hezbollah fighter reacts as he fires a weapon in Western Qalamoun, Syria August 23, 2017. REUTERS/Omar Sanadiki

BEIRUT (Reuters) - The Syrian army and its allies have surrounded Islamic State forces in a second large enclave in the center of the country, a military media unit run by Hezbollah said on Thursday.

The Syrian military advanced south from southern areas of Raqqa province, joining up with their forces north of the town of al-Sukhna in Homs province and in so doing closing the circle around the pocket of IS insurgents.

The IS enclave, located west of al-Sukhna and extending north into Hama province, totals approximately 2,000 square km (770 square miles), according to the Hezbollah military media unit.

The Syrian army secured Al-Sukhna, 50 km (30 miles) northeast of the ancient city of Palmyra, earlier this month. It was the last major town in Homs province held by Islamic State.

Last week, Syrian forces surrounded another large IS enclave in central Syria to the west of the one encircled on Thursday.

The jihadists have lost swathes of Syrian territory to separate campaigns being waged by government forces backed by Russia and Iran, and by the U.S.-backed Syrian Democratic Forces (SDF), which is dominated by the Kurdish YPG militia. The SDF is currently focused on capturing Raqqa city from Islamic State.

Islamic State still controls nearly all of Deir al-Zor province, which is bordered to the east by Iraq. The Syrian government holds a pocket of territory in Deir al-Zor city and a nearby military base.