A Sri Lankan court on Friday jailed former army chief Sarath Fonseka for three years for alleging that the President's brother had ordered the execution of surrendering Tamil rebels.
Fonseka, who ran against President Mahinda Rajapakse in 2010 elections, is already serving a 30-month prison term after a court martial convicted him on corruption charges.
In a 2-1 split verdict, the three-judge Colombo high court bench found Fonseka guilty of violating emergency regulations by "spreading rumours and causing public disorder" in an interview with a weekly newspaper.
He had alleged that the president's brother, defence secretary Gotabhaya Rajapakse, had ordered field commanders to kill white flag-carrying Tamil rebels in the final stages of Sri Lanka's separatist conflict in May 2009.
The defence secretary firmly denied the allegation while giving evidence during the 16-month trial.
Fonseka, who also testified in his defence, insisted that the newspaper had used his comments out of context.
The charges had carried a maximum prison term of up to 20 years.
The three-year sentence specified "rigorous imprisonment" which means he will be expected to perform manual labour.
Security was tight around the Colombo high court ahead of the judgement, with hundreds of armed police guarding the complex.
Fonseka supporters had staged demonstrations during previous hearings and hundreds turned out on Friday to cheer the former army chief as he arrived for the verdict.
A retired four-star general, Fonseka led the Sri Lankan army to its 2009 victory over the Liberation Tigers of Tamil Eelam (LTTE), ending the island's 37-year separatist conflict.
He subsequently fell out with the government and says the legal cases against him are politically motivated.
He faces yet another case in which he is accused of harbouring military deserters who he allegedly used as bodyguards during his failed election challenge against Rajapakse.
He was arrested shortly after the 2010 presidential poll.
In September last year, a court martial sentenced him to 30 months for corruption related to irregularities in military procurements. He also lost the parliamentary seat he won in April 2010 legislative elections.
An earlier court martial had found him guilty of interfering in politics while in uniform and stripped him of his rank and pension.
The United Nations estimates that at least 7,000 ethnic Tamil civilians were killed in the final months of fighting between government troops and the Tamil Tigers.
Fonseka angered the government by saying he would willingly testify before any international tribunal probing possible war crimes charges.
Friday's verdict coincided with President Rajapakse's 66th birthday and the court complex was decorated with huge cut-outs of the president's image.