Three days after his son was shot dead by al-Qaeda militants, Naif Dundar was calm and impassive as he shook hands with a stream of mourners.

Mr Dundar’s son Ferit, 30, was killed with 14 other fighters in an ambush in the intensifying fight in northern Syria between Kurds and the Islamic extremists who have emerged as their main antagonists in the country’s chaotic civil war.

The conflict, little reported amid the wider civil war against the Syrian regime, pits the YPG, a hardened Kurdish guerrilla organisation with 30 years’ fighting experience, against a global jihadi movement with a dreaded reputation.

Ferit and his comrades were killed by Jabhat al-Nusra on the first day of the Muslim holiday of Eid al-Adha, when the YPG had