Rajapaksa also had a head start: His party nominated him weeks before the 52-year-old Premadasa, a cabinet minister in the incumbent government, was named the candidate for the New Democratic Front.
"It is a clear win".
"I am very happy that I have won. He will be sworn in tomorrow or the day after", Mr Rambukwella said. Gotabaya was a key figure during the almost 10-year presidency of his elder brother Mahinda, whose two terms were marked by his authoritarian grip.
However, he lost the Tamil majority civil war affected Northern Province and the Muslim dominated Eastern Province with a vote percentage of 65 to 70 per cent.
(Lanka-e-News 17.Nov.2019, 5.30PM) Issuing a statement Sajith Premadasa said that he has made a decision to resign from his party deputy leadership with immediate effect.
Premadasa has received wide support from minority areas in north and east.
After polls closed, Elections Commission chairman Mahinda Deshappriya said there were "no serious incidents of violence".
The troika had three senior personnel each from India and Sri Lanka on it to coordinate matters relating to the conduct of the war against the separatist militant group the Liberation Tigers of Tamil Eelam (LTTE).
Saturday's poll changed into the predominant recognition check of the United National Celebration (UNP) govt of High Minister Ranil Wickremesinghe who stepped apart and allowed his deputy Premadasa to stand in the election.
Foreign Minister Shah Mahmood Qureshi has also congratulated the newly-elected President of Sri Lanka Gotabaya Rajapaksa. "This development could further erode India's once-dominant influence in Sri Lanka, " adds Chellaney.
Wickremesinghe's administration failed to prevent the April attacks despite prior and detailed intelligence warnings from India, according to a parliamentary investigation.
The Rajapaksas are adored by Sri Lanka's Sinhalese majority for defeating the Tigers and ending a 37-year civil war in 2009 in which around 100,000 people lost their lives.
This makes the brothers detested and feared among many Tamils, who make up 15 percent of the population. The UN estimates that up to 40,000 civilians died in the conflict that began in 1983.
Under his brother, Gotabaya was defence secretary and effectively ran the security forces, allegedly overseeing "death squads" that bumped off rivals, journalists and others. They deny the allegations.
She noted that under another Rajapaksa president, fiscal risks will rise as the country is likely to borrow heavily for more China-backed infrastructure projects.
China in July gifted a warship to Sri Lanka, in a growing sign of its deepening military cooperation with the strategically located island nation in the Indian Ocean. The brothers "spent and spent without giving any consideration to how it has to be paid back", he said.
"Comparatively this is the most peaceful presidential election we have had in this country", Deshapriya told reporters at the end of a 10-hour voting period.
Police said there were no casualties, but two women were injured by the stones.
The counting of votes is continuing and final results are expected by evening.