An explosion outside the Sri Lankan prime minister's office in Colombo has killed 13 people and injured up to 28.

Officials say Prime Minister Sirimavo Bandaranaike was not in her office at the time of the explosion.

A woman seen loitering near the scene apparently detonated the explosives, which were strapped to her body, as security staff were about to question her.

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Hours after the suicide bomb attack, gunmen in the capital killed a minority Tamil leader, Kumar Ponnambalam, of the All Ceylon Tamil Congress.

He was regarded as sympathetic to the Tamil Tiger rebels. It is not known who carried out the shooting.

Two female constables, two policeman and a passer-by were killed immediately in the bomb attack, as well as the bomber.

Another five people died later from their injuries and several more are reported to be in critical condition..

No one has yet claimed responsibility for the attack, which took place at 0900 local (0300GMT).

President's narrow escape

The attack comes less than three weeks after a similar suicide bombing in which President Chandrika Kumaratunga, the prime minister's daughter, narrowly escaped assassination.

The bomb killed 23 people and injured 100 during an election campaign rally.

Mrs Kumaratunga was wounded and may lose the sight in one eye.

Security has been tight in Colombo since then amid fears of more bombings, suspected to be the work of the separatist Tamil Tigers (LTTE).

The LTTE guerrillas are fighting for an independent homeland in the north-east of Sri Lanka.

Over 55,000 people have been killed in the struggle over the past two decades.

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