Smoke rises from central Kobani during fighting between Islamic State militants and Kurdish forces Reuters

The authoritative UK-based Syrian Observatory for Human Rights (SOHR) has corroborated reports that the Islamic State (Isis) launched a fresh attack on the flashpoint city of Kobani from across the border in Turkey.

The offensive began with a suicide bomb attack carried out in an armoured vehicle at the border crossing between Kobani and Turkey by three Islamist militants named Abu Qutaiba, Abu Dhir Al-Turkmani, and Abu Tariq Jazrawi. At least eight Kurdish fighters and 17 Islamic State fighters had been killed in the attack.

A spokesperson for Syria's Kurdish Democratic Union Party said Isis "used to attack the town from three sides" but "today, they are attacking from four sides". It is believed that the vehicle crossed the border from Turkey at around 4am GMT killing two people and injuring others.

Ankara, which has been reluctant to help Kurdish fighters in their fight against Sunni Islamists in Kobani, harshly rebutted the allegations.

"Claims that the vehicle reached the border gate by crossing through Turkish soil are a lie," read a government statement. "Contrary to certain claims, no Turkish official has made any statement claiming that the bomb-loaded vehicle had crossed in from Turkey."

A statement from the Prime Ministry's Directorate General of Press and Information (BYEGM) also refuted the claims.

However. other Kurdish officials and a Kobani-based activist seemed to confirm that Isis assault came from Turkish territory. Kurdish militant Idris Nassan told Reuters the jihadists attacked with two cars but Kurdish fighters "destroyed them before they reached their targets".

Mustafa Bali, who is also based in Kobani, reported that Isis fighters were positioned in grain silos on the Turkish side of the border and were launching attacks toward the border crossing point. "It is now clear that Turkey is openly cooperating with Isis," Bali said.

Meanwhile, a US-led coalition carried out at least 30 airstrikes in Syria against Isis in the northern province of Raqqa, according to SOHR.