The 33-year-old, from the the elite Special Air Service unit, is the first British soldier killed in combat fighting the IS group.

He was embedded with US forces when they were caught by an improvised explosive device on Thursday, the Ministry of Defence (MoD) said.

Tonroe, from Manchester in northwest England, had previously served in Afghanistan and the Middle East.

The blast happened in the northern Syrian city of Manbij, US and British officials said Friday. A US soldier was also killed and five other coalition personnel wounded.

Since 2014, the coalition has provided weapons, training and other support to forces fighting IS in Syria and Iraq.

Tonroe's commanding officer, who was not named by the MoD, said the sergeant was a "deeply intelligent man and one of life's characters".

"He had a steel core, served his country with pride and was a first class soldier, proven in combat, faced risk willingly and was ever ready for more," the CO said.

"He thus died as he lived: daring and fearless in duty. We mourn his loss dearly."

Defence Secretary Gavin Williamson said Tonroe had served Britain with "great distinction" and was exceptionally courageous.

"Sergeant Tonroe fought to protect British values, our freedoms and to keep us back at home safe. His sacrifice, unflinching commitment and bravery will never be forgotten," he said.

Syria's seven-year war has killed more than 350,000 people and displaced millions.

Syria's army promised Saturday to finish off fighters in the final opposition holdout of devastated Eastern Ghouta outside Damascus after a penultimate pocket was declared "empty" of rebels.