Syrian soldiers clashed with Islamic State militants outside a government-controlled army airport on Friday, a British-based monitoring group said, part of a major escalation of fighting between the al Qaeda offshoot and the military.

The hardline Sunni militants have gained ground in Syria over the past five weeks, bolstered by equipment seized in a lightning offensive last month in neighbouring Iraq.

On Thursday, the group seized the Sha’ar oilfield, east of the central city of Homs, in what the Britain-based Syrian Observatory for Human Rights said was one of its bloodiest clashes with President Bashar al-Assad’s forces.  […]