A US-BACKED Syrian force has begun an offensive to capture the northern city of Raqqa, the de facto capital of Daesh, after months of clearing operations.

An American commander said the battle will be long and difficult, but success would deliver a “decisive blow” to the extremists.

By early afternoon yesterday, opposition activists said the Kurdish-led Syrian Democratic Forces (SDF) were trying to break into the city from the east, triggering intense clashes.

Raqqa was among the first cities captured by Daesh in January 2014, and has been the home of some of the group’s most prominent leaders.

Talal Sillo, a spokesman for the SDF, confirmed operations had begun in co-ordination with the US-led coalition.

“We declare today the beginning of the great battle to liberate the city of Raqqa, the alleged capital of terrorism and terrorists,” he said.

“Morale is high and military readiness to implement the military plan is complete.”

SDF fighters began advancing towards Raqqa in November, capturing wide areas of northern Syria from the extremists. Last week, they reached the northern and eastern gates of the city after intense clashes under the cover of US-led air strikes.

Raqqa is currently surrounded from the east, north and west, and opposition activists have reported intense shelling and air strikes on the city since Monday night, which killed at least 12 people.

Daesh militants are not expected to give up easily. Iraqi forces launched an offensive to capture the northern city of Mosul, the largest in that country held by Daesh, in October and heavy fighting continues there.

Lt Gen Steve Townsend, the top US commander in Iraq, said the twin offensives against Mosul and Raqqa are harming Daesh’s prestige and ability to recruit new loyalists.

“It’s hard to convince new recruits that Daesh is a winning cause when they just lost their twin ‘capitals’ in both Iraq and Syria,” he said.

He added US-led coalition forces will continue to support the SDF in Raqqa, providing equipment and training.