Sirisena and his new Prime Minister Ranil Wickremesinghe, who till now was the leader of opposition, both took the oath of office in the Independence Square.
Wickremesinghe had met Rajapaksa in the morning when he conceded defeat and gave an assurance of smooth transition of power.

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Sirisena, 63, was officially elected as the sixth President of Sri Lanka by Commissioner of Elections Mahinda Deshapriya.

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He polled 6,217,162 or 51.2 percent of the vote against the incumbent Rajapaksa's 5,768,090 or 47.6 percent.

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Sirisena, backed by the main opposition United National Party (UNP), the Buddhist nationalist JHU or the Heritage Party and a host of other Tamil and Muslim minority parties, defeated Rajapaksa in a keenly contest battle.

Rajapaksa, 69, called a snap Presidential election to win a mandate for his third term. Hailing from the rural north central province, Sirisena does not speak English, is ever seen in the national dress.

He has no background of hobnobbing with the Colombo elite and socialites. No old boy of a leading Colombo school, he was more than a match for Rajapaksa's rural appeal.

READ MORE: Sri Lanka votes in tightest election in decades

"What was expected to be an easy win for him turned into a difficult task when Sirisena broke ranks in late November to challenge Rajapaksa as the opposition unity candidate," political experts said.

Sirisena ran his campaign based on a 100-day reform programme to introduce constitutional and democratic reforms.

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He has pledged a national unity government with the participation of all political parties represented in parliament. Rajapaksa left his tightly guarded official residence early on Friday morning in order to facilitate Sirisena's induction.

Sirisena said he wished to thank Rajapaksa and urged the new President's supporters to celebrate victory peacefully.

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