Colombo - Sri Lankan President Mahinda Rajapaksa and his former health minister were among 19 people on Monday to hand in nominations to contest the island's presidential election next month.The papers from the 19 were handed in to Elections Commissioner Mahinda Deshapriya after Rajapaksa called the election to seek an unprecedented third term, two years before his second term ends.Rajapaksa was first elected in 2005 and won re-election in 2009 and he is seeking a third mandate endorsing his performance amid criticism locally and internationally.His administration is accused of corruption, nepotism and shrinking democratic processes, and he faces a United Nations inquiry into war crimes allegedly committed in ending a 25-year separatist war.Main challenger"I will win, I know the people are with me, it's very clear," Rajapaksa told reporters outside the elections office.Rajapaksa's former health minister and party No 2, Maithripala Sirisena, has become his main challenger and he is now backed by the main opposition United National Party.Sirisena has accused Rajapaksa of misusing his all-powerful presidency, and has vowed to abolish the president's executive powers, and strengthen the Parliament and judiciary if he is elected."I will be committed to bring about the changes the country needs," Sirisena said. "It is clear that we will achieve a magnificent victory. With that we will wipe out family rule, strengthen freedom and democracy and build up a country free of corruption and fear."Possibility of violenceThree of Rajapaksa's brothers hold top positions— one as a Cabinet minister, another as Parliament speaker and a third as a powerful defence secretary controlling the armed forces. Rajapaksa's elder son and a niece are lawmakers and there are other relatives in the government bureaucracy and diplomatic positions.Deshapriya rejected objections raised against the candidacies of both Rajapaksa and Sirisena, saying their applications were within the rules. But the commissioner expressed concern over election violence that has broken out, and advised candidates and supporters to respect election laws.He urged media outlets and government officials to act impartially and said his office will monitor media reporting.Several opposition supporters and their homes have been attacked since Sirisena defected from Rajapaksa and announced his candidacy last month.The election is 8 January, just five days before Pope Francis arrives in the country for a three-day visit. The closeness between the election and the papal visit and the possibility of violence has prompted some Catholic clergy to seek a postponement of the visit.