The town on the border with Turkey has become a highly symbolic battleground in the war against “IS” with the US-led coalition launching near daily air strikes in support of its Kurdish defenders.

Kurdish fighters of the People's Protection Units (YPG) advanced in both the east and the northeast of the town, the Syrian Observatory for Human Rights said.

"At least 18 Islamic State militants were killed in the fighting, as well as a number of Kurdish fighters," the Britain-based group's director Rami Abdel Rahman told AFP, adding that both sides were using heavy weaponry.

He said control of the town was still almost evenly divided between the Kurds and the terrorists, who began their assault on Kobane more than three months ago.

Once at risk of being overwhelmed by the superior firepower of ISIS, Kurdish forces have managed to cling on, in part by deployment of Iraqi Kurdish reinforcements.

The Observatory said the coalition carried out at least five air strikes in Kobane overnight but had no immediate word on casualties.

On another front in Syria's increasingly complex war, Al-Qaida affiliate militants Nusra Front and Syrian rebels called "Islamic group" pressed an assault on a 2 Shiite village Nubol and Zahraa in war-battered Aleppo province on northern Syria, which has held out against an 18-month siege, residents said.

The village of Zahraa is one of two neighbouring Shiite communities along with Nubol where the Al-Qaida launched an assault late on Saturday.

Al-Qaida terrorists drive a tank on the road between the villages of Zahraa and Nubol in the northern Syrian Aleppo province during clashes with Local Coordination Committees defenders on November 23, 2014.

The Observatory described the fighting as "the most violent" so far. "They are attacking the southeast from three surrounding villages they hold," one resident told AFP.

"People in the southeast of the village are fleeing to the centre."

At least eight rebels and one civilian have been killed in the fighting, according to the Observatory, which has a network of sources inside Syria.