Islamic State (Isis) militants have launched an offensive on Ras al-Ain (or Ayn) on the Syrian-Turkish border causing fierce clashes with the Kurdish YPG (People's Protection Units).

Hundreds of IS members, with the support of tanks and heavy vehicles, carried out the attack on the strategic town in the Hassakeh province leaving dozens of dead on both sides.

Local reports from Ras al-Ain said that more than 45 YPG fighters have been killed and dozens captured by IS. The assault started when IS launched a surprise attack on the village of Tel Khanzir, some 21km west of Ras al-Ain and seized it.

Aziz Dawoud, civil rights activists from the town, told ARA Nesws that the village has a strategic hill overlooking two roads linking Tel Khanzir with Mabrouka Hanadi and Tel Abyad in Raqqa province.

Ras al-Ain was at the heart of fighting in 2013 before Kurdish forces ousted rebels and al-Qaida-linked jihadists from the town. It has a border crossing with Ceylanpinar in Turkey.

The attack seems to be part of a wider strategic offensive on the Hassakeh province, in north-eastern Syria. Last month, during a three-day attack, IS took 10 villages inhabited by the ancient Christian minority of the Assyrians and abducted at least 250 people, including women and children. At least 1,000 Assyrian families escaped the IS attack and fled to Kurdish-hold Qamishli and Hassakeh cities.

A spokesman for the Democratic Union Party (PYD), the YPG's political arm, confirmed the intense battles.