Eleven policemen were killed and more than 20 others including four civilians were injured in an attack on a police post in north eastern Sri Lanka as Tamil guerrillas have begun to step up their attacks ahead of the upcoming elections, military officials said.

More than 30 guerrillas stormed the Muttur Police post in the Trincomalee district around 2.00 p.m. after firing mortars and rocket propelled grenades at the post and thereafter briefly took control of the place until reinforcements came and re-captured the post.

The post situated at the 64th mile post was manned by about 30 to 35 policemen and soldiers at the time of the attack. Military officials said the attack was a complete surprise and a rare type of attack as the guerrillas carry out this type of attack only at nights or towards dawn.

Among the injured were 10 policemen, six soldiers and the remaining civilians. All of them were transferred to the Muttur hospital or the Trincomalee hospital which is situated across the lagoon.

Military officials said that the guerrillas also had removed some of the weapons and ammunition from the camp. "Police and army reinforcements were rushed from the area and the police post has been re-established with a bigger strength", a senior police officer based in the area said.

The attack came less than two days after guerrillas attacked an oil tanker off the northern coast virtually destroying the tanker which was carrying fuel to the security forces and civilians in the north.

On Monday a Tamil suicide bomber exploded himself at a location close to where Prime Minister Ratnasiri Wickramanayake was attending a public function. Police strongly believes that the bomber was waiting for the premier.

Police and security forces have been placed on full alert in the run up to the December 5 elections.