Former president Mahinda Rajapaksa's attempt to stage a comeback in Sri Lanka's general election has ended in defeat as results showed the alliance that toppled him making decisive gains.

The ruling United National Party (UNP) was likely to fall just short of an outright majority but Prime Minister Ranil Wickremesinghe should still command enough support to form a stable government.

"I offer my grateful thanks to all parties and individuals who worked untiringly during the election period to ensure victory for the people," Wickremesinghe, 66, said in a statement on Tuesday.

"Let us together build a civilised society, build a consensual government and create a new country."

If confirmed, the outcome would be a triumph for President Maithripala Sirisena, who beat his former ally Rajapaksa in a presidential vote in January and called early parliamentary polls to secure a stronger mandate for reforms. Rajapaksa was Sri Lanka's president for nine years until his January 8 election defeat.
 
Defeat for Rajapaksa will keep Sri Lanka on a non-aligned foreign policy course and loosen its ties with China, which during his rule pumped billions of dollars into turning the Indian Ocean island into a maritime outpost.

Victory over former mentor

With results from 18 of Sri Lanka's 22 districts in, Wickremesinghe's UNP had won about 105 seats in the 225-seat parliament. 

A total of 196 seats are up for grabs in multi-member constituencies with a further 29 to be allocated by proportional representation in the 225-seat chamber.

Since his surprise victory over his former mentor, Sirisena has struggled to impose his authority over his United People's Freedom Alliance (UPFA) party and was powerless to prevent Rajapakse's Sri Lanka Freedom Party (SLFP), from standing as one of its candidates.

Sirisena threatened to invoke his executive powers to prevent his combative predecessor from becoming prime minister, but Rajapakse was banking on a strong showing to force Sirisena to back down.

Rajapaksa was hailed a warrior king for defeating Tamil Tiger separatists to end a nearly 26-year civil war. But he is accused of using his popularity to take control of parliament, the courts, the armed forces and all government institutions.

He was also accused of widespread human rights abuses and of suppressing freedoms.

Elections Commissioner Mahinda Deshapriya said the vote had been one of the most peaceful in Sri Lanka's history. About 70 per cent of the 15 million registered voters voted in Monday's elections.

Police spokesman Ruwan Gunasekara said 35 people were arrested countrywide for election law violations.

The mood on the streets was subdued on Tuesday, with celebrations and street processions banned for a week after the polls under Sri Lankan election laws.

Source: Agencies