Pro-government activists attacked by bomber on motorcycle in an eastern district.
Police said the man who detonated the explosives was a suspected member of the Liberation Tigers of Tamil Eelam (LTTE), and may have planned to carry out the attack somewhere else.
“We had information from a man we arrested the previous day about a possible arms storage location of the Tigers and we moved in this morning to check,” a policeman at the scene said.
He also said that they had found several hand grenades and three jackets filled with explosives to be worn by suicide bombers.
According to Udaya Nanayakkara, a military spokesman, “the man came out of a house while the search operation was underway and detonated [the] explosives he was carrying.”
“Police and security forces were there when the blast went off.”
Authorities have tightened security on buses, trains and various neigbhourhoods in Colombo, as well as other ethnic Sinhalese-majority areas after a series of bomb blasts the military says has killed at least 90 people this year.
Defence ministry figures point to at least 1,600 LTTE fighters killed this year. At least 94 soldiers and police have also been killed in 2008.
But casualty figures provided by both sides differ vastly and cannot be independently verified.
The Sri Lankan government bars journalists and human rights workers from the front line and LTTE-held areas.