Colombo - Sri Lanka's president asked minority Tamils to "forget the past" as he campaigned for re-election on Thursday, vowing not to allow another uprising after decades of ethnic war.President Mahinda Rajapakse, who is seeking an unprecedented third term, told a public rally in the former war zone of Mullaittivu that Tamils should join him to rebuild the battle-scarred region.He made no reference to allegations that his troops killed some 40 000 Tamil civilians in the final months of fighting, when the leadership of the Tamil Tiger separatists was wiped out."Let us unite. Forget the past. Let us develop this country together," he said in an address broadcast live."We cannot let history repeat in this country."Sri Lanka faces a UN-mandated international probe into war crimes. A report is expected at the UN Human Rights Council in March.The UN has estimated that at least 100 000 people were killed in Sri Lanka's separatist war between 1972 and 2009.Rajapakse included a few lines of Tamil in his address in Mullaittivu, where government forces fought their final battles with the separatist Liberation Tigers of Tamil Eelam (LTTE).Local and foreign rights groups say despite the end of the war local Tamils are under constant surveillance in a region where the military still maintains a high presence.King-makersTamils account for about 15% of the electorate and could emerge as king-makers in January's presidential election if the majority Sinhalese are split between Rajapakse and his main rival.The president faces an unexpected challenge from his former health minister and party general secretary, Maithripala Sirisena, who, like Rajapakse, is a member of the majority Sinhalese community.Rajapakse, aged 69, was seen as the favourite when last month he called the January 8 snap election two years ahead of schedule.But Sirisena has emerged as a formidable opponent after securing the support of all main opposition groups.The popularity of Rajapakse's party showed a 21 percentage point decline at local elections in September.Rajapakse has announced hefty salary increases for public servants, drastically reduced water, electricity and fuel prices in the run-up to the vote.He has also offered subsidised motorcycles to hundreds of thousands of public servants and granted free electricity and water to police officers living in official barracks.