Fighters from the Islamic State group have launched a new offensive on the northern Syrian town of Kobani after shelling the area from their positions nearby, activists said.

Heavy fighting took place in Kobani and a large number of mortar shells were fired into the town. Machine gun fire could be heard from inside the town where black smoke was billowing.

The US Central Command said an airstrike destroyed an IS artillery piece near Kobani. This afternoon, warplanes of the US-led coalition could be heard flying over Kobani.

Idriss Nassan, a senior official in Kobani, said the fighting concentrated on the southern and eastern edges of the town, also known as Ayn Arab.

"They think they can enter the city and these are just dreams," said Nassan adding that IS fighters have not been able to take Kobani despite more than a month of attacks.

The Britain-based Syrian Observatory for Human Rights said the fighting concentrated on the eastern side of the town, surrounded on three sides by Islamic State fighters. It added that IS fighters were spreading news in areas under their control that they will take Kobani on Saturday.

IS launched its offensive on Kobani in mid-September and captured dozens of villages before entering parts of the town. The fighting has forced 200,000 people to flee to neighbouring Turkey from the fighting.

Earlier this week, the US Central Command said its forces conducted more than 135 airstrikes against the militants in and around Kobani, killing hundreds of IS fighters.

The Observatory and Aleppo-based activist Ahamd al-Ahmad said that the area near the northern village of Handarat witnessed intense clashes between Syrian rebels and government forces.

Government forces are trying to cut a main road linking rebel-held neighbourhoods of Aleppo, Syria's largest city, with those in the countryside, Al-Ahmad said via Skype.

The Observatory said the fighting near Handarat has left 15 soldiers and pro-government gunmen dead as well as 12 opposition fighters since the early hours of today.