Updated

Sri Lanka's main Tamil party Tuesday demanded troops be confined to barracks after accusing them of campaigning for the ruling party at key elections in the former separatist stronghold of Jaffna.

The Tamil National Alliance (TNA) told President Mahinda Rajapakse that soldiers were campaigning for his United People's Freedom Alliance (UPFA) in the Jaffna peninsula, where the minority party was expected to do well.

The TNA said soldiers were also selectively discouraging Tamils in TNA strongholds from voting at the region's first ever provincial council election, scheduled for September 21.

The vote is in line with Colombo's promise to the international community to share limited power with ethnic Tamils through a local council after the military crushed separatist Tamil Tiger rebels in May, 2009.

The Sinhalese-dominated government is under international pressure to promote ethnic reconciliation and investigate allegations of war crimes by its forces in the final stages of the war.

It has denied what the UN calls "credible allegations" that up to 40,000 civilians were killed during the bloody finale.

The TNA said the military continued to engage in civilian activities and were clearly trying to influence the 714,000-strong mainly Tamil electorate, and support candidates of Rajapakse's UPFA.

"What has been objectionable even before the announcement of the polls is not only the presence of the military but the fact that they without invitation engage with the civilian population in many exclusively civilian matters," the TNA said.

TNA leader R. Sampanthan in his letter said election authorities were unable to stop the military involvement in the region.

"It is clear that there cannot be a free and fair election if the military continues its interfering presence in the Northern Province," Sampanthan said in his letter to Rajapakse.

"It has thus become imperative for me to ask you to relegate the army and the other security forces to the barracks immediately and leave the maintenance of law and order in the hands of the police."

There was no immediate comment from the president's office, but the military denied it was engaged in election propaganda work.

"These allegations are baseless," military spokesman Ruwan Wanigasooriya told AFP. "We have been engaging in civil affairs since the end of the war and have always worked at the invitation of the people.

"Our involvement continues, but it is to a lesser extent than what it was in 2010 and 2012. I totally deny that the army is engaged in political activity."