Defence officials said military units were sent to areas in provinces where police expected trouble during voting. The police are activating 64,000 men for election duty.

"We will intensify mobile patrols and call in the military to assist police," said police deputy Inspector-General Jayantha Wickremaratne.

The election, the third in four years, was called by President Chandrika Kumaratunga to end her power struggle with Prime Minister Ranil Wickremesinghe and differences over his handling of a Norwegian-backed effort to seek a political settlement with Tamil Tiger rebels.

Kumaratunga accused the premier, who is from a rival party, of conceding too much to the Tamil Tigers in talks aimed at halting the conflict that has claimed more than 60,000 lives since 1972.

The Tigers are expected to gain political clout after Friday's election in which 12.89 million people are eligible to vote a system of proportional representation.

The Tigers are not in the running but their Tamil National Alliance (TNA) proxies are expected to win about 15 to 18 seats from the 225 up for grabs.

They could emerge as kingmakers with analysts predicting a hung parliament as the parties of Kumaratunga and Wickremesinghe run neck and neck.

A minority government would be at the mercy of the world's most ruthless guerrillas who have been branded "terrorists" by many countries, including the United States and India.

For Wickremesinghe, the election is a referendum on his peace drive with the Tamil Tigers.

The return of his market-friendly United National Party (UNP) could push Sri Lanka back to the same uneasy cohabitation arrangement that brought about Friday's vote in the first place.

But Wickremesinghe played down fears of a constitutional gridlock.