Sri Lanka's ex-army chief General Sarath Fonseka said Thursday that the two courts martial and other cases against him were 'politically motivated'.

'The court martial has been set up by President Mahinda Rajapaksa for no other reason, but to put me in jail and kill me politically,' Fonseka said at his court martial, on charges of favouring a company owned by his son-in-law supplying equipment to the army.

Another court martial has already convicted Fonseka of involvement in politics while serving as the commander of the army before June 2009. He was dishonourably discharged from the army as a punishment.

He faces three other cases in civilian courts, including one for allegedly conspiring against the government.

The ex-army chief spearheaded the military campaign against Tamil rebels. He later fell out with Rajapaksa and went on to challenge him at the Jan 26 presidential elections but lost. Fonseka was arrested two weeks later.

Since then Fonseka has been in custody, but he contested parliamentary elections for a political party backed by the Marxist JVP in April and was elected.

Fonseka told the court martial that he had no faith in the tribunal.

'I certainly know that I will not get justice from this court martial and irrespective of the evidence in this case I will be convicted and jailed,' he said.

'The people of this country are the best judges and they know what I have done for this country, taking risks on my own life on a number occasions,' he said. Fonseka survived a Tamil rebel suicide attack in 2006.

His comments came as parliament Wednesday passed constitutional amendments enabling Rajapaksa to run for a third term as president after completing his second term in 2016.

The amendments also give the president additional powers to appoint officials to key posts in the judiciary, police and election commission, a task previously performed by an independent body.