Sri Lanka's military Thursday rejected opposition allegations that it had deployed troops to campaign for President Mahinda Rajapakse's re-election.

Military spokesman Brigadier Ruwan Wanigasooriya denied opposition claims that soldiers were distributing material in support of the President who is seeking an unprecedented third term at the January 8 elections.

"The statement that the army has employed soldiers for election-related propaganda is baseless and extremely presumptuous," Wanigasooriya said.

The main opposition United National Party (UNP) Thursday accused army chief Daya Ratnayake of deploying troops to campaign for Rajapakse and said his conduct will be reported to the international community.

"The deployment of soldiers for such political work is destroying the dignity of the uniform," UNP spokesman Mangala Samaraweera told reporters in Colombo Thursday.

He accused the army chief of including election propaganda leaflets in soldiers' pay packets last month, an allegation denied by Brigadier Wanigasooriya.

Wanigasooriya told AFP they would investigate the claim if the opposition provided "information on any such instances".

Rajapakse, who is also the commander in chief of armed forces, faces allegations that his troops killed at least 40,000 Tamil civilians in the final stages of the country's Tamil separatist war in 2009. Colombo has resisted international moves to probe Colombo's war record.

Rajapakse called the snap election two years ahead of schedule after his party's popularity dropped a sharp 21 points at a local election in September.

The Brussels-based International Crisis Group said in a report last week that Rajapakse was facing an unexpectedly strong challenge from his former health minister Sirisena, who has secured wide opposition support.

"The sudden emergence of a strong opposition candidate caught many, including President Rajapakse, by surprise," the ICG said.

It warned the election could turn ugly and called for the international community to send monitors to observe the campaign and deter any violence.

Both the election chief and private monitors have accused the government of exploiting state assets as well as personnel in support of the president.