The November 16 elections have revived debate about the end of a long-running bloody separatist conflict, with army troops accused of massacring up to 40,000 civilians in 2009 while crushing Tamil Tigers rebels.

The Election Commission said it wanted Lieutenant General Shavendra Silva to explain his appearance in full-page newspaper advertisements supporting Rajapakse, who was defence secretary at the time of the alleged atrocities.

The advertisements quoted Silva as saying Rajapakse was "extremely efficient" and "addressed the urgent need of the security forces... during the final stages of the conflict".

"It is an election law violation for a serving military officer to endorse a candidate and engage in political activity," Election Commission Chairman Mahinda Deshapriya said.

Silva could face up to three years in jail and a fine over the advertisements.

Rajapakse's campaign team denied being behind the adverts, although they appeared with party colours in a newspaper that openly supports him.

There was no immediate comment from Silva.

Rajapakse said Tuesday that if elected he would not honour commitments made to the UN by a previous government to investigate alleged atrocities committed while he was defence secretary during his brother Mahinda Rajapakse's decade as president.

At that time, Silva was a brigadier leading attacks against the rebels, and was known to be closely associated with the Rajapakses.

Silva's appointment in August sparked international outrage because of his links to alleged war crimes, and the UN suspended the recruitment of Sri Lankan troops for peacekeeping duties.