The military said on Saturday a bomb blast blamed on separatist Tamil Tigers has wounded 45 people in Sri Lanka's capital.

Military spokesman Brigadier Udaya Nanayakkara has accused the Tamil rebels of setting off the Saturday blast in the heart of capital Colombo.

Nanayakkara said the rebels are desperate because of defeats in the northern front lines and are targeting civilians.

Hospital spokesman Dr Anil Jasinghe said 45 wounded people are receiving treatment, mostly for minor injuries. There is no immediate comment from rebels on the blast.

Sri Lanka is immersed in a decades-long civil war. Fighting has escalated in recent months, with the military capturing a series of rebel bases and large chunks of territory.

Officials have reiterated a pledge to crush the guerrillas by the end of the year.