At least 23 people were killed in a suicide blast in Sri Lanka

The blast, immediately blamed on the Tamil Tigers, also injured at least 80 people, the military said.

The bomber struck during the opening of a new office for the opposition United National Party (UNP) in the north central town of Anuradhapura, 124 miles north of the capital Colombo, attended by retired Major-General Janaka Perera, who led many successful campaigns against the separatist Tamil guerrillas in the country's 25-year-long civil war.

Last month Mr Perera unsuccessfully ran to be North Central Province's chief minister, a powerful local position.

The opposition accused the government of ignoring repeated requests for better security for Mr Perera - an open critic of the way Colombo has conducted its military campaign against the rebels.

Anuradhapura is huge tourist draw and home to some of Sri Lankan Buddhism's holiest sites. For a millennium it was the seat of the kingdom of the Sinhalese, who make up 75 per cent of the Indian Ocean island's 21 million people.

It has many ancient ruins, but is also a hub of major military operations to supply the war zone further north.