At least 36 quarry workers were killed early today in northern Kenya by suspected Islamic extremists from Somalia, Kenyan police say. The killings happened in Mandera County near the border with Somalia and the attackers escaped, a local police chief says. The workers were ambushed at the quarry as they slept by gunmen who singled out non-Muslims and killed them, according to police sources, who say some workers were shot dead and others were decapitated. No group has yet claimed responsibility for the killings, but the attack bears the hallmarks of Somalia's Islamic militant rebels, al-Shabab, who hijacked a bus in the same county last week. In that attack, 28 non-Muslims were separated from other passengers and shot dead. (More Kenya stories.)