Military activity in the area has been monitored by the US military and intelligence who have concluded that four

Pentagon and State Department officials refused to comment on the reports. The Russian defence ministry said all missiles fired at targets in Syria on Thursday had reached their targets.

The US secretary of state, John Kerry, had a 30-minute telephone call with his Russian counterpart, Sergei Lavrov, to express concern that Russia’s targets in Syria were not related to Islamic State.

“The secretary repeated our concerns about the preponderance of targets that are being struck by Russian military forces that are not Isil-related,” said a spokesman, John Kirby, using an alternative acronym for Isis.

There were “no tactical-level decisions” made during the call, Kirby added.

He also said he could not confirm reports that Russian missiles had crashed in Iran.
“I can’t confirm it but I think it points all the more towards the need to have proper deconfliction procedures in place.”

Ashton Carter, the US defence secretary, predicted earlier that Russia would suffer casualties “within the coming days” as it deepened its military involvement in Syria

There have been signs that Saudi Arabia and its Gulf allies are preparing to counter the Russian attack.

Nato’s secretary general, Jens Stoltenberg, said the military alliance was ready to defend Turkey against threats after violations of its airspace by Russian jets conducting the airstrikes against Syria.

Nato is thought to be boosting its response forces to be able to deploy troops quickly