BEIRUT - Air strikes thought to have been carried out by Russian jets on a rebel-held residential area in northwestern Syria have killed 51 civilians, a Britain-based monitor said on Friday.

Nine children were among those killed when the strikes hit the Zardana area of Idlib province late Thursday, the Syrian Observatory for Human Rights said.

Observatory head Rami Abdel Rahman said the toll was rising because more bodies had been found under the rubble of houses destroyed in the air strikes. Dozens were wounded, he said.

The Russian defence ministry dismissed the Observatory’s reports of strikes on Zardana as having “nothing to do with reality”, in a statement carried by Russia’s TASS news agency.

Zardana is largely controlled by Islamist rebels, with a small presence of the Hayat Tahrir al-Sham alliance led by Syria’s former Al-Qaeda affiliate. An AFP correspondent at the scene saw volunteers with a crane still searching the rubble. Half a dozen men in civilian clothes helped carry a person in a black body bag away from the site of the strikes, which pulverised several buildings.

Most of Idlib province is held by an array of Islamist and militant groups with only parts controlled by the Russian-backed government.

IS militants retake parts of Syria town in major attack

The Islamic State group seized parts of a key town on the Syrian-Iraqi border Friday in a massive operation that further confirmed the militants remain a force on the ground.

IS used at least 10 suicide bombers in its offensive on Albu Kamal, which lies in he Euphrates Valley in eastern Syria and swiftly took several neighbourhoods, the Syrian Observatory for Human Rights said.

The offensive is the latest in a string of IS attacks which confirm predictions that the militant organisation would continue to be a threat even after the collapse of its “caliphate” last year.

Quitting Syria too soon would be a ‘blunder’: Mattis

US Secretary of Defence Jim Mattis warned Friday it would be a “strategic blunder” to pull out of Syria before UN-led peace efforts had made progress.

A US-led coalition is conducting military operations against the Islamic State group in Syria and Mattis said they must not leave a “vacuum” that President Bashar al-Assad and his Russian and Iranian allies could take advantage of.

Talks in Geneva led by UN Special Envoy Staffan de Mistura have made little headway, but Mattis said they must be given the chance to succeed.

“In Syria, leaving the field before the special envoy Staffan de Mistura achieves success in advancing the Geneva political process we all signed for under the UN security council resolution would be a strategic blunder, undercutting our diplomats and giving the terrorists the opportunity to recover,” Mattis said at a meeting of coalition defence ministers at NATO headquarters in Brussels.

IS seized parts of a town on the Syria-Iraq border on Friday in the latest in a string of attacks that comes as the continued presence of coalition forces in Syria is coming into question.

US President Donald Trump has vowed he would pull out his troops from Syria but Mattis has pleaded for a more patient approach.