At least eight Islamic State (IS) militants were killed in Syria by Turkish artillery fire and US-led coalition airstrikes, an official said on Thursday.Some IS weapons systems, including mortar positions, were also destroyed in the operation, Xinhua news agency reported.Turkey is set to deploy new air defence systems in its southeastern province of Kilis, as rocket attacks from IS held regions across the border in northern Syria have killed over 21 people in the province this year.