In an unrelated incident on Monday, the Syrian government accused the US of bombing a Syrian military base in eastern Syria and killing three soldiers. The Central Command rejected the allegation. Brett McGurk, the US special envoy for the coalition, said on Sunday on Twitter that there had been no coalition air strikes within 50 kilometres of the claimed incident.

The Syrian Observatory for Human Rights monitoring group reported that jets likely to be from the coalition hit part of the Saeqa military camp near the town of Ayyash in Deir al-Zor province, killing four Syrian army personnel.

But a US military official, speaking on condition of anonymity, said the US is certain that Russia was responsible for the deadly strike on the Syrian army camp.

Russia, a key ally of Syria, is waging its own air campaign in support of Dr Assad, and has also been striking in Deir al-Zor.

A second US military official said indications pointed to a strike carried out by a Russian Tu-22 bomber.

Meanwhile, Canada’s new Liberal government has said it will act within weeks on its campaign promise to withdraw six fighter jets that have been attacking IS positions in Iraq and Syria.

The Liberals, who took power last month, say Canada can contribute more effectively to the US-led campaign by assigning more troops to train Kurdish fighters in northern Iraq.

“It’s a matter of weeks, not months,” Foreign Minister Stephane Dion told reporters when asked when the jets would be pulled out. “We’re carrying out two per cent of the air strikes. We’re going to do something more efficient for the coalition.”

MCT, Reuters