China on Friday downplayed the impact of Sri Lanka's presidential election upset, dismissing suggestions that the stunning win by Maithripala Sirisena could shake up Beijing's plans in the Indian Ocean.

Sirisena on Thursday ousted longtime president Mahinda Rajapakse, who has relied heavily on Chinese funding for major infrastructure work in his island country.

Maithripala Sirisena will be sworn in as Sri Lanka's new president Friday after the strongman incumbent conceded defeat in a bitterly fought election, brought down by charges of corruption and growing authoritarianism.

A top aide to Mahinda Rajapakse said the outgoing president accepted the decision of voters who turned out in force on Thursday, in a remarkable turnaround for a leader who had appeared certain of victory when he called snap polls in November.

Sri Lankans turned out in large numbers Thursday, shrugging off some reports of voter intimidation to vote in the island's tightest election in decades as President Mahinda Rajapakse battles for survival.

Turnout was higher than expected in Tamil-dominated areas of the north and east, which have boycotted national elections in the past and where resentment against Rajapakse runs high.

Sri Lanka's election commission said Wednesday it is investigating claims that troops are being deployed in the Tamil-dominated north before a closely-fought presidential vote that has already been marred by violence.

Chief election commissioner Mahinda Deshapriya said there had been complaints security forces were deploying in the northern Wanni region, in contravention of election laws.

International observers said Sunday they had received complaints of voter intimidation before this week's Sri Lankan presidential election, in which the incumbent faces a tough battle to win an unprecedented third term.

The 55-member panel of monitors told reporters they had already received complaints that the military had set up 400 roadblocks to discourage minority Tamils from voting freely in former war zones.

Campaign-related violence escalated across Sri Lanka ahead of next week's elections as President Mahinda Rajapakse fights an unexpectedly tough battle to remain in power, poll monitors and police said Saturday.

The private Campaign for Free and Fair Elections (CaFFE) monitoring group said it had received 1,073 complaints since campaigning got underway in early December.

Sri Lanka's main opposition presidential candidate narrowly escaped a stoning by suspected pro-government activists at a rally Friday, but at least 20 of his supporters were seriously injured in the attack days ahead of the vote.

Rocks and stones were hurled into the crowd of some 20,000 people during a speech by Maithripala Sirisena, who is mounting a serious challenge against President Mahinda Rajapakse, on Friday evening.

Sri Lanka Friday warned the European Union not to be "prescriptive" about next week's presidential elections after Colombo-based ambassadors urged the government to ensure a peaceful election.

The Ministry of External affairs took objection to a statement issued earlier Friday by Colombo-based European ambassadors that Sri Lankans should be "free to choose their leaders without violence or fear."

Sri Lanka's embattled President Mahinda Rajapakse urged minority Tamils to back him in next week's election, calling himself the "known devil", as he made a final push for votes in the country's former war zone Friday.

While he remains popular among ethnic majority Sinhalese voters, Rajapakse is widely detested by members of the country's biggest minority after overseeing the brutal crushing of a 37-year Tamil rebellion.

Sri Lanka's opposition Thursday accused the government of deploying thousands of troops to deter ethnic minority Tamils from voting against President Mahinda Rajapakse in next week's election. 

A top opposition official said the sending of reinforcements to Tamil-majority areas was part of a strategy to intimidate voters against backing Rajapakse's main challenger Maithripala Sirisena in the January 8 contest.