COLOMBO: Sri Lanka's former army chief Sarath Fonseka was due to be released from jail later on Monday, officials said, after he was detained in 2010 shortly after challenging the president in elections.

Fonseka, who led government troops to victory over the separatist Tamil Tiger rebel forces in 2009 ending decades of bloodshed on the island, has served more than two years in military custody and prison.

President Mahinda Rajapakse last week ordered an official pardon for Fonseka, 61, who was on Monday being taken from hospital back to jail after two weeks of treatment for a respiratory ailment.

Fonseka fell out with Rajapakse over who should take credit for winning the war against the Tamil rebels and he quit the army before campaigning unsuccessfully in the 2010 presidential election against Rajapakse.

Two weeks after his poll defeat, Fonseka was detained on a charge of corruption relating to military procurements. He was given a 30-month jail sentence in September 2010.

Presidential spokesman Bandula Jayasekera said that papers confirming Fonseka's release were being sent to the Ministry of Justice on Monday.

Doctors who declined to be named confirmed that Fonseka had been discharged from hospital.

In November, Fonseka was sentenced to three more years in jail for saying that Tiger rebels who surrendered had been killed on the orders of the president's brother Gotabhaya Rajapakse, who is defence secretary.

Fonseka has also angered the government by saying he would testify before any international tribunal probing possible war crimes charges after the United Nations said thousands of civilians were killed in the last months of fighting.

The former general was regarded by Washington as a political prisoner and US officials had repeatedly called for his release.

The Democratic National Alliance (DNA) party that Fonseka founded to contest the 2010 general elections currently has just three seats in the 225-member parliament.