A female Kurdish fighter has carried out a suicide attack in the besieged Syrian town of Kobane, killing an unknown number of fighters from the Islamic State in Iraq and the Levant (ISIL), a monitoring group has said.

The Syrian Observatory for Human Rights said the woman blew herself up at an ISIL position east of Kobane on Sunday, detonating a grenade that was in her possession, killing ISIL fighters in the process.

"The operation caused deaths, but there is no confirmed number," observatory director Rami Abdel Rahman said.

The monitor said the woman was a commander in the female unit of the People's Protection Units, known by its Kurdish initials YPG, which had stormed an ISIL gathering on the eastern outskirts of the town.

The UK-based group said it was the first reported instance of a female Kurdish fighter carrying out a suicide bombing against ISIL, which has itself often favoured the tactic.

Al Jazeera cannot independently verify the group's report.

The attack comes as ISIL fighters continue their offensive on Kobane, despite US-led airstrikes and a renewed push against them by Syrian Kurdish fighters.

Idris Nahsen, a deputy minister of the Kurdish region, told the AFP news agency that US air raids on ISIL were not enough to stop them taking the town.

"They are not enough to defeat terrorist groups. The strikes are helping but we need heavy weaponry, armoured vehicles, cannons, rockets. They are one kilometre away in some places and two or three kilometres in others".

The observatory and the Kurdish People's Protection Unit, known by its Kurdish initials YPG, which is fighting ISIL, said heavy clashes raged overnight as the US-led coalition launched air raids on ISIL positions around Kobane.

The YPG told Al Jazeera that about 20 ISIL fighters and 10 YPG fighters were killed in the clashes.

Shelling could be heard from the Turkish side of the border, and pillars of smoke rose over the town.

Fighting for Kobane has raged for weeks after ISIL captured dozens of surrounding villages along the Syria-Turkey border.

At least 186,000 people have crossed the border to Turkey, according to the government, and are now sheltering in refugee camps.