An ISIS suicide bomber detonated a truck laden with explosives on Monday in the besieged Kurdish town of Kobani, near the Turkish border crossing with Syria, a monitoring group and Kurdish sources said.

The attack took place in a northern district of Kobani, which has been the scene of heavy clashes between Kurdish forces and ISIS fighters.

Idris Nassan, a Kurdish official in Kobani, said two Kurdish fighters had been wounded during the suicide bomb attack, which appeared to have been aimed at clearing a way for the ISIS fighters to advance further into the town.

"They (ISIS fighters) tried to advance towards the (border) crossing but the (Kurdish) People's Protection Units repelled them ... and they were not able to push forward," Nassan told Reuters.

The Syrian Observatory for Human Rights monitoring group reported more heavy clashes on Monday inside the city, where U.S.-led air strikes have so far failed to halt the militants' advance.

The Observatory said there had been at least five U.S.-led strikes early on Monday, mainly targeting southern districts of Kobani, which is known as Ayn al-Arab in Arabic.

Clashes also continued to the east, killing a dozen ISIS militants, the Observatory said.

The militant group wants to seize the town to consolidate a dramatic sweep across northern Iraq and Syria.