Gotabaya Rajapaksa (left) is a close confidante of the president
Sri Lanka is considering taking action against defeated presidential candidate Sarath Fonseka, the defence secretary has told the BBC.
Gotabaya Rajapaksa - the brother of President Mahinda Rajapaksa - said that Gen Fonseka had allegedly divulged sensitive information to the public.
His comments came just a day after the president was re-elected.
Gen Fonseka has rejected the result and told the BBC that he wants to leave the country because of death threats.
"The government has informed the airport not to allow me to leave the country," he told the BBC Sinhala service. "I fear that an assassination attempt may be made against me."
The defence secretary told the BBC's Anbarasan Ethirajan in Colombo that he was angry with Gen Fonseka for making false allegations against him in public.
Mr Rajapaksa said that Gen Fonseka was wrong to suggest in a newspaper interview that he had ordered the killings of three senior Tamil Tiger rebels as they tried to surrender in the final stages of the conflict last May.
Gen Fonseka later retracted his statement and said his words were taken out of context.
But in his BBC interview, Mr Rajapaksa said the retraction was not enough.
"He accused me of saying that I gave wrong orders. It came out in the newspapers. So we will follow legal procedures. If he has violated certain laws then we will take action.
"He had done many mistakes, remember. He was a member of the security council. He only left three months ago. He divulged certain security information to the public. He did a wrong thing there.
"But we will not arrest him because he was the opposition candidate."
There has been no immediate response from Gen Fonseka to Mr Rajapaksa's comments.
'Free of threats'
In a separate development, Mr Rajapaksa announced that the man believed to be second-in-command of the Tamil Tigers' overseas operations had been arrested.
He said the suspect, known as Rajan (alias Subramaniam Sivakumar) "had been arrested in a South-East Asian nation" and brought to Colombo on Thursday.
He said that the information regarding the suspect came from Tamil Tiger leader Kumaran Pathmanathan, who is currently being held in Colombo.
Mr Pathmanathan was arrested last August.
Earlier, President Rajapaksa said that his clear victory in Tuesday's presidential elections had answered his critics.
The president won six million votes compared to the four million cast for Gen Fonseka.
"The people of Sri Lanka, democratically and very clearly, have shown that they are now free of threats, free of fear, free of terrorism - and they have shown they support the measures which have freed them."
Mr Rajapaksa told reporters that he would start by focusing on the economic development of the country.
He also promised to focus on the concerns of Sri Lanka's Tamil minority and to discuss devolution of power - a subject his opponents have accused him of failing to address.
"From today onward, I am the president of everyone, whether they voted for me or not."
Analysts had predicted a closely fought contest between the two architects of the government's victory over the Tamil Tiger rebels last year.
But in the end President Rajapaksa won the vote comfortably - capturing 57% of the vote in Tuesday's polling, while Sarath Fonseka won 40%, according to the election commission.
The independent Centre for Monitoring Election Violence said that while there were reports of irregularities, there was no evidence to suggest large-scale fraud.
Some 70% of Sri Lanka's 14 million-strong electorate turned out to vote. However, turnout in the Tamil areas in the north-east, where the fiercest fighting occurred during the conflict, was less than 30%.