Sri Lankan President Mahinda Rajapakse said he was confident he would be returned to power as he cast his ballot in presidential elections from his constituency in Hambantota in the south of the island.

"We will have a resounding victory. That is very clear. From tomorrow, we will start implementing our manifesto," he told the media.

Sri Lanka goes to the polls today to elect a new president in the most closely fought presidential race in the country for decades as incumbent Mahinda Rajapaksa seeks a record third term amid a flurry of defections and criticism over his authoritarian rule.

Sixty-nine-year-old Rajapaksa's decision to call early elections in the hope of an easy victory over a fragmented opposition now appears a tough task with a broad coalition of parties rallying behind his former associate turned rival, Maithripala Sirisena.