Sri Lankan presidential candidate Gotabaya Rajapaksa of the Podujana Peramuna (People's Front) party on Sunday claimed victory over his main rival Sajith Premadasa of the National Democratic Front party.
A spokesperson for Rajapaksa claimed success for the former civil war-era defense secretary ahead of official results being announced following Saturday's presidential election.
With more than 40% of the votes counted, Rajapaksa has received at least 51.7% support.
More results due
Results from Rajapaksa's core support base, Sri Lanka's Sinhalese-majority regions were yet to be finalized. But the retired lieutenant colonel, nicknamed the Terminator, was expected to remain firmly ahead.
Rajapaksa is the younger brother of the charismatic but controversial Mahinda Rajapaksa, who was president from 2005-15, including during the government's final victory of the Tamil Tigers in 2009.
Support for Premadasa trailed at some 44%. He had strong support in minority Tamil areas and a poor showing in larger Sinhalese constituencies.
Premadasa has conceded the vote to the opposition candidate.
"It is my privilege to honor the decision of the people and congratulate Mr. Gotabaya Rajapaksa on his election as the seventh President of Sri Lanka," said the ruling party candidate.
The election commission has said the final tally would be announced by Sunday evening.
Sri Lanka's Centre for Monitoring Election Violence reported at least 69 incidents of violence taking place on election day. Gunmen purportedly shot at buses transporting Muslim voters in Anuradhapura district, 180 kilometers north of the capital, Columbo.
However, chairman of the Elections Commission Mahinda Deshapriya said this did not impact attendance. Voter turnout was at a record 85%, with 15.9 million Sri Lankans casting their vote.
Police heavily secured polling areas and say no further incidences occurred after polls had closed.
Suppression of the Tamil Tigers separatist group in 2009 ended nearly 30 years of civil war in Sri Lanka and earned the Rajapaksa brothers widespread support from the country's Sinhalese Buddhist majority. The UN estimates that up to 40,000 civilians died in the conflict that began in 1983.
For the presidential election, Rakapsa ran a nationalist campaign that similarly promised to crush religious extremism and increase security.
Earlier this year, 259 people, including 45 foreigners, died in a series of suicide bombings carried out on Easter Sunday in Sri Lanka. Jihadi militants inspired by the Islamic State carried out the attack.
Critics have accused the Rajapaksas of overseeing human rights violations during the war, including condoning the rape and murder of citizens. The former defense chief and his brother deny such charges.
He has said that, if elected, he would appoint his brother as prime minister and pardon military commanders charged with human rights violations.
Some minority groups are uneasy about his return to power.