Sri Lankan soldiers clashed with separatist Tamil Tiger rebels in a series of battles across the country's embattled north, killing 18 guerrillas, the military said Saturday. Army troops infiltrated a rebel-held area in northern Jaffna peninsula and destroyed two bunkers Saturday morning, killing five Tamil tigers, an official at the defense ministry's information center said on condition of anonymity, citing government policy. He said the soldiers did not suffer any casualties. The military's claim could not be independently verified and Tamil Tiger spokesman Rasiah Ilanthirayan could not be reached immediately for comment, the Associated Press reported. Meanwhile on Friday, soldiers fired artillery and mortar rounds at a farm-type tractor carrying rebels across a defense line in the village of Kilali in Jaffna and killed eight of the guerrillas, the official said. Both the Tigers and the army often use farm-type tractors to tow trailers hauling fighters in battle front areas. Three more rebels were killed in separate clashes in Vavuniya district south of Kilali, the official said. In the neighboring Welioya region, soldiers fired artillery and mortar rounds at a group of rebels, killing two.