The bomb, placed between two vehicles in a parking lot in Colombo's busy Pettah neighborhood, exploded shortly after noon and slightly wounded three bystanders, said military spokesman Brig.
Udaya Nanayakkara. The Tamil Tigers, who have been accused of scores of bombings and other attacks on civilians, were suspected in the blast, he said.
On Monday evening, a hand grenade exploded in Kattankudy, a predominantly Muslim town in eastern Sri Lanka, wounding 21 people, Nanayakkara said. He said it was unclear who was behind the attack.
Meanwhile, air force helicopters attacked rebel bunker lines Monday in support of ground troops in the Kilinochchi district, the military said.
In fighting Sunday, troops captured part of a strategic road in the district after a seven-hour battle that killed seven rebels and one soldier, the military said in a statement.
Attacks on rebel bunkers and other scattered fighting killed 11 rebels in the Welioya, Jaffna and Vavuniya districts, it said.
Two other rebels were killed in a brief clash in Ampara in the east, which the government ousted the rebels from last year, the military said.
With nearly all communications to the north severed, rebel spokesmen could not be contacted for comment.
It was not possible to verify the military's reports because most journalists and other independent observers are barred from the war zone. Both sides often exaggerate their enemy's losses and underreport their own.
Also Monday, the military said a soldier who had been wounded in a rebel suicide attack Sunday in the northern town of Vavuniya died from his injuries.
The Tamil Tigers have fought since 1983 to create an independent state for Sri Lanka's minority Tamils following decades of marginalization by governments dominated by the Sinhalese majority.
