Kurdish fighters backed by US-led air strikes battled Islamic State jihadists for control of a key Syrian town Sunday, while Turkey evacuated some border areas as mortar fire spilled over.

ISIS fighters seized part of a strategic hill overlooking the town of Kobane late on Saturday, a monitor said, but their progress was slowed by new strikes from the coalition of Washington and Arab allies.

A Kobane local official, Idris Nahsen, said ISIS fighters were just one kilometre (less than a mile) from the town and that air strikes alone were not enough to stop them.

He complained of a lack of coordination between the coalition and Kurdish fighters of the ground.

The dusty border town has become a crucial battleground in the international fight against ISIS, which sparked further outrage this weekend with the release of a video showing the beheading of Briton Alan Henning.