COLOMBO: Sri Lanka's opposition warned Saturday of possible vote-rigging and violence by the ruling party in next week's presidential election as both sides wound up campaigning.

Ahead of final campaign rallies later on Saturday, opposition candidate Sarath Fonseka predicted that the ruling party, led by President Mahinda Rajapakse, would use violence to intimidate his supporters in Tuesday's vote.

"They want to create violence and discourage people from voting. A lower turnout will help rigging," he told reporters, adding he expected fake voters and forged ballot papers to also be used.

In the run-up to the poll, police say at least four people have been killed and hundreds wounded in clashes between rival supporters. The house of an influential opposition figure was bombed on Friday.

Fonseka said he and his allies would rely on the protection of the security forces, most of whom he said would vote for him except for a few senior figures who are "trying to please the government."

"We can't counter violence with violence. We have to abide by the law," he said.

Sri Lanka's government has denied it has been behind the wave of election-related unrest and Rajapakse's office said Friday that he was "gravely concerned" over the escalating violence.

"Instructions have been given to the authorities to bolster security at sensitive locations and all political events up to and on polling day to ensure that all Sri Lankans can participate safely in the electoral process," the government said in a statement.

Independent election commissioner Dayananda Dissanayake told reporters Friday he would order a re-poll if any violence was used against voters.

Fonseka, a former army chief, fielded a series of questions about the possibility of an army coup against him if he wins the vote and the movement of armoured vehicles into Colombo as tension rose in the capital.

But he said there would be no popular support for a coup and that he had full confidence in the army.

A group of Fonseka supporters wearing green caps and party T-shirts walked noisily behind a procession of rickshaws on the streets outside the venue of his press conference.

Fonseka and Rajapakse were to finish campaigning at rallies planned in and around Colombo later Saturday.

Poll officials said all arrangements were in place to conduct the election although less than a sixth of the 300,000 ethnic Tamil war-displaced civilians had applied to vote.

Elections chief Dissanayake said he was arranging 1,000 buses for ethnic Tamils in the island's former war zones to travel to polling booths on Tuesday because of fears that they may not have enough public transport.

Both Rajapakse and Fonseka are members of the majority Sinhalese community which is seen split between the two men. In the event of a close contest, the minority Tamil vote is seen as being a crucial deciding factor.

Tuesday's election, the first peace-time presidential poll, takes place after a bitter, intensely personal campaign between the architects of the country's victory over rebel forces in May.

President Rajapakse told reporters last week that the campaign failed to bring about an informed debate on issues and instead had degenerated into "mud slinging," a charge made by Fonseka too.

Rajapakse handpicked Fonseka to be his army chief in 2005 and the two men were victorious allies on the battlefield last year against the Tamil Tiger rebels but are now sworn enemies at the ballot box.

The poll marks the first time in 37 years that Sri Lankans have gone to polls without the influence of the Tigers, who fought a brutal war for a Tamil homeland before being crushed by government forces in May.