ISIS fighters had sent reinforcements of fighters and weapons into Tabqa in anticipation of a fierce battle to defend the town.

An ISIS counter-attack on Syrian regime forces advancing towards an extremist stronghold on Monday left 28 combatants dead, a monitor said.

Dozens of ISIS fighters early on Monday attacked government positions south of the town of Tabqa, an ISIS stronghold on the Euphrates River, said the Syrian Observatory for Human Rights.

Observatory head Rami Abdel Rahman said fierce clashes broke out, but that regime forces were able to maintain their positions and were still 15 kilometers (10 miles) from the ISIS-held Tabqa airport.

“Eleven regime fighters and 17 Daesh fighters were killed in the attack,” said Abdel Rahman, using the Arabic acronym for ISIS.

Earlier this month, government fighters backed by Russian air power began pushing north towards Tabqa, held by ISIS since 2014.

The town lies some 50 kilometers (31 miles) east of the extremist group’s Syrian de facto capital of Raqa city, and recapturing it would sever the supply road from the west.

Last week, ISIS fighters had sent reinforcements of fighters and weapons into Tabqa in anticipation of a fierce battle to defend the town.

Abdel Rahman said a total of 37 government fighters and 101 ISIS militants have been killed since the regime launched its offensive for Tabqa.

The war in Syria — which began with the brutal repression of anti-government demonstrations in 2011 — has killed more than 280,000 people and displaced millions.

It has evolved into a brutal, complex civil war among the government, rebels, extremists, and Kurds, each carving out zones of control.

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