"If any rights have been violated (during the war), justice will be ensured through a transparent domestic judicial mechanism," Rajapaksa said in his election manifesto.
He, however, reiterated that he would not cooperate with a UN-mandated investigation into the government's 2009 defeat of the Tamil Tiger rebellion.
The promise of a probe by 69-year-old Rajapaksa is being seen as a response to similar pledges made by his main challenger Maithripala Sirisena, 63.
Rajapaksa did not make it clear how such a probe would be different from an inquiry he ordered in July amid intense international pressure to account for the 2009 killing of Tamil civilians.
President Rajapaksa has called a snap election on January 8, two years ahead of the schedule.
The Tamil Tigers were defeated after their leader Velupillai Prabhakaran was killed by the Sri Lankan forces in 2009.
Sri Lanka has come under increased scrutiny from international organisations for its rights accountability during the last phase of the conflict.
The island-country has been subjected to three UN Human Rights Council resolutions since 2013.
The last resolution in March this year advocated the setting up of an international investigation on alleged war crimes committed by both sides during the conflict. The government continues to resist any such probe.
An estimated 80,000–100,000 people had died during the nearly three decades-long conflict between the government forces and Liberation Tigers of Tamil Eelam (LTTE).

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