Police at the scene of the blast
A suicide bomber has killed at least nine people and wounded 90 in Sri Lanka's capital Colombo, the army says.
Seven of those killed were police. The bomber rammed a motorcycle into their bus near a five-star hotel in the busy central business district.
President Mahinda Rajapaksa blamed Tamil Tiger rebels, accusing them of "cowardice and brutality". There was no immediate word from the rebels.
Violence has grown since the government pulled out of a truce this year.
Army spokesman Brigadier Udaya Nanayakkara told the BBC that the dead included three women police constables.
Dozens of civilians are among the wounded.
'Like an earthquake'
The blast in Colombo's Fort district, near the Hilton Hotel, happened at around 1230 local time (0700 GMT).
Ekanjith Rawwalage, head of customer services at the hotel, told BBC News that the blast took place near a police checkpoint outside the hotel.
"It was a loud explosion. It felt like an earthquake," said Mr Rawwalage.
He said some window panes of the hotel had been damaged by the explosion, but all the guests were safe and the hotel gates had been shut.
Mr Rawwalage said he had seen ambulances rushing the injured to the hospital.
The area is also the site of the official residence of Sri Lanka's president and has been targeted in the past by Tamil Tiger rebels.
Large numbers of security personnel were in the area preparing for opposition protests against recent provincial elections in eastern Sri Lanka.
Many of the injured are in a serious condition
(Photo: Elmo Fernando)
The demonstrations came ahead of the swearing in at the presidential secretariat of the new eastern province chief minister, Pillaiyan, a former rebel who defected.
"We were there with the riot squad getting ready for the opposition demonstration," one policeman told the BBC. "We heard something hitting the bus. Then the bus blew up in flames."
"I saw a ball of fire crushing the bus," said another. He was receiving treatment for leg wounds in hospital.
The Tigers have fought for a generation for an independent state for the Tamil minority in the island's north and east.
About 70,000 people have been killed since the civil war began in 1983.