COLOMBO (AFP) - A court martial in Sri Lanka convicted former army chief Sarath Fonseka on Friday of corruption and sentenced him to three years, a top military official told AFP. The military court, whose decision must now be ratified by President Mahinda Rajapakse, found that Fonseka favoured an arms company run by his son-in-law, said the official, who asked not to be named. He was charged on four counts of corrupt purchases for the military. There was no immediate comment from Fonsekas Democratic National Alliance (DNA) party which has maintained that the prosecution of the former four-star general is part of a political vendetta. State radio said Fonseka could appeal to a civilian court against his three-year jail term. Fonseka, 59, who led the military to victory over Tamil Tiger rebels in May last year, fell out with the government and unsuccessfully tried to unseat Rajapakse in January polls. The chairman of the court read out its decision and it must now be ratified by the president, the official said, adding that the closed-door court would make no formal announcement. Rajapakse is expected to ratify the decision - seen as a formality - when he returns from the United Nations general assembly session this month. Fonsekas lawyers had refused to make final submissions in the former army chiefs defence after accusing the court of serious irregularities. Fonseka was arrested two weeks after his defeat in the presidential elections and has remained in military custody since. He won a seat in parliamentary elections in April, however, allowing him to attend parliament. He has said the government is seeking revenge for his decision to stand against the president and to keep him from speaking in parliament. They are going to put me in jail and I am prepared for that, Fonseka told reporters in parliament after being escorted by the military from his room in Colombos naval headquarters to parliament in August. The first court martial also ordered the withdrawal of the medals he had earned during his 40-year military career and stripped him of his rank and pension. He faces civilian charges of employing army deserters, as well as revealing state secrets - offences that carry a 20-year jail term.