COLOMBO: A Tamil Tiger suicide bomber triggered a blast near offices of the main opposition party in northern Sri Lanka on Monday, killing at least 22 people, officials said.

The attack at a bus stop in the town of Anuradhapura comes as the Sri Lankan military appears on the verge of capturing the Tigers' key northern headquarters as part of a major offensive in the drawn out ethnic conflict.

Several members of the United National Party were among those killed in the bomb blast which also left 80 people injured, the defence ministry said. "The LTTE (Liberation Tigers of Tamil Eelam) set off a suicide explosion. There are large numbers of casualties.

At least 22 are dead and 80 injured," said military spokesman Brigadier Udaya Nanayakkara. The United National Party's Ranil Wickremensinghe was prime minister in February 2002 when Colombo and Tiger rebels negotiated their Norwegian brokered peace process, which finally collapsed earlier this year.