Colombo, Nov. 17 -- Sri Lanka's former wartime defence chief Gotabaya Rajapaksa was set to become president after his main rival conceded defeat on Sunday in an election that came months after bombings by Islamist militants threw the country into turmoil.

Rajapaksa, who oversaw the military defeat of Tamil separatists under his brother and then president Mahinda Rajapaksa 10 years ago, has promised strong leadership to secure the island of 22 million people, the majority of whom are Sinhalese Buddhists.

With half the votes counted from Saturday's election, Rajapaksa led with 50.7 percent, while his main rival Sajith Premadasa had 43.8 percent, the election commission said. Rajapaksa's party claimed victory.

Premadasa, a housing ministe...