Sri Lanka's detained ex-army chief Sarath Fonseka today filed nomination papers as a candidate of a new opposition alliance for the April 8 Parliamentary poll. The poll is set to witness a three-cornered fight also involving the ruling UPFA and former premier Ranil Wickremesinghe's UNF. <br/> <br/>59-year-old Fonseka filed his nomination from the Colombo District constituency under the Democratic National Alliance (DNA) this morning and it has been accepted by the Election Commission, said Somawansa Amarsinghe, the chief of Marxist JVP, which is a key constituent of DNA.<br/><br/>Today was the last day for filing nomination papers.<br/><br/>Fonseka's papers were filed by DNA General Secretary Vijitha Herath. Campaigning has already begun for the crucial polls, which are being held more than two months after the January 26 Presidential election in which incumbent Mahinda Rajapaksa defeated Fonseka, who was the candidate of the joint opposition.<br/><br/>Fonseka's wife Anoma will join the campaigning for DNA soon. Fonseka, who was arrested on conspiracy charges, is being detained at the Naval Headquarters.<br/>