"The Tamil National Alliance extends to the people of Sri Lanka - in particular to the people of the North-East - its sincere thanks for extending their overwhelming support to President-elect Sirisena in accordance with the advice of the TNA," a statement from the TNA leader Rajavayothi Sampanthan said.
"The new President Sirisena has to address urgently many grave issues the country faces, including an honorable resolution of the national question so as to enable the minority Tamil speaking people of Sri Lanka to be true beneficiaries of democracy," the statement added.
The Tamils, who account for 13 per cent of the electorate, angered by Rajapaksa's brutual military campaign that crushed the LTTE, voted for the opposition unity candidate Sirisena.
The main Tamil party support along with the support of Sri Lanka Muslim Congress (SLMC) enabled Srisena to defeat the powerful incumbent Mahinda Rajapaksa in yesterday's presidential election.
About 75 per cent of the 15.04 million electorate voted in election called two years ahead of schedule by Rajapaksa, who was confident of securing a record third term.