Deadly blast hits Sri Lanka bus

At least 20 people have been killed in a bomb explosion targeting a bus in the Sri Lankan capital of Colombo.

At least 40 others were injured in the blast in a southern suburb of the city.

The explosion comes as the Sri Lankan army continues a large-scale offensive against Tamil Tiger separatists in the north of the country.

Officials have blamed the rebels for a string of recent attacks on public transport, including a train bombing that killed eight people last week.

Military spokesman Brig Udaya Nananyakkara said the Tamil Tiger rebels had detonated a roadside bomb that targeted the bus in the suburb of Moratuwa.

Eyewitnesses said they said they saw bodies inside the bus, which had shrapnel marks all over.

There have been a number of bomb attacks in Colombo recently blamed on the Tamil Tigers.

On Wednesday, at least 24 people were injured when a packed commuter train in the city was hit by a bomb.

And the Tamil Tigers were blamed for last week's bomb attack at Dehiwela station that left at least eight dead.

In February, 11 people died in a suicide attack at Colombo's main train station.

In northern Sri Lanka the military is carrying out an offensive aimed at crushing the rebels by the end of this year.

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.