They said Gotabhaya Rajapakse, 70, who served in the cabinet when his brother Mahinda Rajapaksa was president for nearly a decade until 2015, will stand for the newly formed Sri Lanka Podujana Peramuna (SLPP) party.

Mahinda is barred from running again by a constitutional provision which limits presidential terms to two.

Another brother and former minister, Basil Rajapakse, told reporters in Colombo that Mahinda would be the leader of the new party.

Ex-defence chief Gotabhaya was in charge when security forces crushed Tamil rebels and ended a 37-year-long separatist war in May 2009.

The no-holds-barred military campaign also triggered allegations of grave human rights abuses, including the killing of up to 40,000 Tamil civilians in the final months of fighting.

Gotabhaya is currently on bail facing prosecution for allegedly siphoning off millions of rupees of state cash to build a monument for his parents when his brother was president.

He is also facing a civil suit in the United States for allegedly causing the death of a prominent anti-establishment newspaper editor in Sri Lanka in January 2009.

He reportedly had dual citizenship, but renounced his US nationality earlier this year to clear the way to enter the presidential race.

The SLPP is a breakaway faction of the Sri Lanka Freedom Party (SLFP), which is nominally led by current President Maithripala Sirisena.

Highlighting frequent schisms in the country's politics, the SLFP in turn broke away from a coalition with Prime Minister Ranil Wickremesinghe's right-wing United National Party (UNP) earlier this year.

Wickremesinghe has indicated he too wants to run for president, but his party is yet to nominate an official candidate amid major internal clashes over his leadership.

Incumbent Sirisena also plans to run again.