Maithripala Sirisena, Sri Lanka's new president, sworn in

New Sri Lankan President Maithripala Sirisena was sworn into office Friday and vowed to curtail the powers amassed by his predecessor, who was swept aside in a stunning election upset.

Sirisena, a longtime political insider and an ally of former President Mahinda Rajapaksa until just a few weeks ago won the Thursday election by capitalizing on Rajapaksa's unpopularity among the island nation's ethnic and religious minorities, as well as grumbling among the Sinhalese majority about his family's growing power.

"With this victory we will implement the 100-day program in our election manifesto," Sirisena told jubilant crowds in Colombo after his swearing-in. Sirisena had promised to change Sri Lanka's Constitution to drastically reduce the power of the president and return the country to a parliamentary system with a prime minister as its leader.

Sirisena also promised that he would not run again for president.

He thanked Rajapaksa for conceding defeat but called for future campaigns to be "much more mature," and blasted the state media for its coverage.

"Even though they carried out character assassination and vilified me, I can say I had the maturity to bear it all as a result of my long political experience," he said.

Popularity rose after defeating Tigers

He took the oath of office with senior Supreme Court Justice Kanagasabapathy Sripavan, bypassing the country's chief justice, who was installed by Rajapaksa in a widely criticized move to expand his authority even more.

Sirisena then swore in opposition leader Ranil Wickremesinghe as the prime minister.

While Rajapaksa's campaign centred around his victory over the Tamil Tiger rebels in 2009 and his work rebuilding the country's infrastructure, Sirisena's focused on reining in the president's expanding powers. He also accused Rajapaksa of corruption, a charge the president denied.

Rajapaksa's power grew immensely after he defeated the Tigers, using his huge popularity among the Sinhalese, many of whom hailed him as a king. He used his parliamentary majority to scrap a constitutional two-term limit for the president and gave himself the right to appoint many top officials.

He also installed numerous relatives in top government positions, sidelining the party's old guard, which helped give rise to the revolt that brought Sirisena to power.

One of Rajapaksa's brothers is a Cabinet minister, another is the speaker of Parliament and a third is the defence secretary. One of his sons is a member of Parliament and a nephew is a provincial chief minister. The diplomatic service was full of his relatives and friends.

'Peaceful conduct' praised

Sirisenareceived 51.2 per cent of the votes in Thursday's election and Rajapaksa got 47.5 per cent, said Elections Commissioner Mahinda Deshapriya. Rajapaksa had conceded defeat and vacated his official residence early Friday morning, hours before the official announcement.

Sirisena called on his supporters earlier Friday to remain peaceful in the wake of victory, telling them at a gathering at the Election Commission that they shouldn't "even hurt anybody's feelings."

"The honour of this victory is in your peaceful conduct," he said.

U.S. President Barack Obama praised the peaceful transfer of power and said the United States looked forward to deepening its ties with Sri Lanka.

"Beyond the significance of this election to Sri Lanka, it is also a symbol of hope for those who support democracy all around the world. International and domestic monitors and observers were permitted to do their jobs. Sri Lankans from all segments of society cast their ballots peacefully, and the voice of the people was respected," he said in a statement.

Jagath Dissanayake, a 40-year-old businessman, said people had voted against corruption.

"We can't give a vote of gratitude to him every day," he said, referring to Rajapaksa's war victory.