Heavily-armoured fighters for the Islamic State (also known as Isis) have seized 16 key Kurdish villages in northern Syria near the Turkish border, winning regional battles that have lasted more than a year.

Clashes between Isis and Kurdish militants resulted in several casualties on both sides, with Kurdish civilians eventually forced to flee to safer areas for fear of mass atrocities by jihadists akin to the ones committed in Iraq.

According to Nawaf Khalil, spokesman for Syria's Kurdish Democratic Union Party, the Kurdish fighters left or lost up to 20 villages in the Kobani region, also known as Ayn Arab. While urging the world to come to Syria to help the Kurds, Khalil called the battles in Kobani "the most violent" and noted that Sunni Islamists were using tanks in the attack.

Earlier this week, in other parts of Syria, Kurdish fighters captured 14 villages from Isis, showing that momentum in the Syrian civil war may change abruptly. But the retreat in the Kobani region is still a worrying sign for a US-led coalition which is scrambling to help Kurdish forces to fight against the Isis threat.

It is also a setback for the People's Protection Units, known by the initials YPK, which until now have managed to contain Isis in Syria and even open a safe passage from Iraq for members of the ancient religious and ethnic Yazidi minority, who were threatened by Sunni militants.

US airstrikes against Isis in Iraq have been going on since early August 2014 under the authorisation of president Barack Obama. Last week, he ordered strikes agianst Sunni militants in Syria as well.