A bomb targeting a bus in the Sri Lankan capital, Colombo, has killed at least four people and injured another 20, police and military officials say.
A Claymore landmine is said to have been used for the blast
The blast took place as the military bus was passing a busy junction in a district that houses key military installations, reports said.
A hospital official told Reuters that two of those killed were soldiers.
Military officials said they suspected the separatist Tamil Tigers. The rebels denied involvement, Reuters reported.
The powerful explosion took place near Hotel Nippon in Colombo's commercial Slave Island area.
Victims were taken to the Colombo national hospital, where several people were reportedly in a critical condition.
"There was a Claymore [landmine] attack targeting an army bus carrying troops," a military official at the scene told Reuters.
The official said there were "about 11 soldiers" on board the bus.
Most of the victims were civilians while a few soldiers were also admitted with shrapnel injuries, the AFP news agency quoted hospital director Hector Weerasinghe as saying.
Police and eyewitnesses said the low-budget Nippon hotel suffered extensive damage and staff members were also among those wounded.
Fighting between troops and the rebels, who want independence for minority Tamils in the north and east, has worsened in recent months.
A Norwegian-brokered ceasefire in 2002 broke down two years ago, resulting in renewed fighting that has killed more than 5,000 people.
At least 70,000 people have died since the war began in 1983.