(KUNA) -- Three Sri Lankan policemen and a civilian were killed while 10 people were injured by a claymore mine triggered by Tamil rebels in north-eastern Sri Lanka Monday. The explosion occurred in Trincomalee, 240 km northeast of the capital Colombo, news agency Indo-Asian News Service reported. Sri Lankan Police have blamed the Tamil rebels of the Liberation Tigers of Tamil Eelam (LTTE) for the explosion.In another incident, LTTE injured two police officers in the eastern Sri Lankan town of Batticaloa in a grenade attack, the news agency reported.