Syrian government forces used newly arrived Russian warplanes to bombard Islamic State insurgents in Aleppo province in northern Syria, a group monitoring the civil war said on Thursday, in an attempt to break a siege on a nearby air base.

Russia is bolstering its ally Damascus against rebels with military aid that U.S. officials say has included fighter jets, helicopter gunships, artillery and ground forces.

The air strikes, which began earlier this week, were accompanied by ground attacks near the Kweiris air base in the east of Aleppo province, where government troops have long been surrounded by Islamist militants, the Britain-based Syrian Observatory for Human Rights said. […]