At least 15 people have been killed in two bomb blasts at separate election rallies in the Sri Lankan capital Colombo.

At the first, the country's President, Chandrika Kumaratunga, received minor injuries and was taken to hospital.

Shortly after the blast, a second explosion at an opposition election rally outside Colombo left three people dead, including a former army officer.

A government official said President Kumaratunga was not seriously hurt in the first explosion and was in no danger.

At least 12 people died in the first blast and there were reports that the country's justice and transport ministers had been hurt. Forty people are reported wounded.

The Sri Lankan defence ministry has announced an indefinite curfew in the capital and surrounding districts following the explosions.

Police said that a female suicide bomber attempted to approach President Kumaratunga after she had left the rally stage, but was prevented from doing so by body guards.

State television said the president suffered minor injuries and a police spokesman quoted doctors as saying she appeared to be in shock.

Mrs Kumaratunga, of the People's Alliance, is seeking a second term in office in Tuesday's elections.

She is pitted against Ranil Wickremesinghe of the opposition United National Party and 11 other candidates.

The explosions come on the last day of a violent election campaign.

Officials say five people have been killed and many more wounded in election related violence which has also included an assassination attempt on Mr Wickremesinghe.

Political violence

The explosions are just the latest in a long series of politically-motivated bomb attacks in Sri Lanka.

Most have been blamed on Tamil separatists who are fighting for a homeland in the north of the country.

Mrs Kamaratunga came to power in 1994 promising to end the civil war.

However, the Tamil Tiger rebels broke off peace talks a year later, and since then she has been considered a potential target for the separatists.

Previous attacks include the one which killed President Ranasinghe Premadasa at a rally in 1993.

In 1987 a car bomb explosion in Colombo killed more than 100 people.

Heavy fighting in the north

The attacks coincide with more heavy fighting in northern Sri Lanka between troops and Tamil Tigers in the area around the strategically-important Elephant Pass.

The government said troops had defended an army base against a sea-borne attack yesterday by guerrillas in speedboats.

It said more than 100 guerrillas had been killed, but it acknowledged losing eighteen soldiers, with nearly 60 others wounded.

The Tamil Tigers have made several attempts recently to capture the base, which guards a causeway linking most of Sri Lanka to the Jaffna peninsula - a former Tiger stronghold.