ANKARA (Reuters) - Artillery fire from Turkey and air strikes by U.S.-led coalition warplanes killed at least eight Islamic State fighters in northern Syria, military sources said on Thursday.

They said Turkish army howitzers and multiple rocket launchers fired on the militants on Wednesday as they were preparing to strike Turkey with rockets and mortars, destroying one defensive fighting position.

The coalition has stepped up air strikes against Islamic State in the area in recent weeks, in response to rocket attacks by the militants on the Turkish border town of Kilis.

Kilis, just across the frontier from an Islamic State-controlled region of Syria, has been hit by rockets more than 70 times this year. More than 20 people have been killed and parts of the town reduced to rubble.

(Reporting by Tulay Karadeniz; Writing by Daren Butler; Editing by Nick Tattersall)