A suicide bomber ignited a blast on Friday when police knocked on a house door during a sweep targeting Tamil rebels in Sri Lanka's capital and the explosion wounded seven people, including three police officers, the military said.
Police officers were searching a neighborhood in the northern part of Colombo for Tamil Tiger rebels suspected of infiltrating the capital and had just knocked on a door of a house at dawn when the blast was triggered inside, military spokesman Brig. Udaya Nanayakkara said.
The blast killed the bomber and wounded seven other people, including three police officers, he said.
He blamed the Tigers for the blast. The group could not immediately be reached for comment. It routinely denies responsibility for such attacks.
Three policemen and four civilians were being treated at Colombo National Hospital, said Anil Jasinghe, a doctor at the hospital. An Associated Press photographer at the scene saw the blown-off head of the suicide bomber on the concrete roof of the adjoining building.
Authorities have stepped up security searches on buses and trains and in neigbhoorhoods of Colombo and other ethnic Sinhalese-majority areas after a series of bomb blasts killed about 90 civilians so far this year, according to the military.
The Tamil Tigers, listed as a terror group by the US and European Union, are blamed for more than 240 suicide attacks against political, military and economic targets during their long separatist campaign.
Violence has escalated on this Indian Ocean Island since the government withdrew from a 2002 cease-fire with Tamil rebels last month.
Tamil Tiger rebels have fought the government since 1983 to create a separate homeland for the country's ethnic minority Tamils. More than 70,000 people have been killed in the conflict.