TEHRAN (AFP) - Iran implicitly denied Thursday (March 26) that a missing former FBI agent had died in its custody as his family claims, restating its longstanding position that he left the Islamic republic "years ago".

US President Donald Trump did not confirm Mr Bob Levinson's death, saying that Iran had not communicated any news on the former agent, who has been missing since 2007 and would have turned 72 this month.

"Based on credible evidence, (Levinson) left Iran years ago for an unknown destination," foreign ministry spokesman Abbas Mousavi said in a statement.

He added that Iran had done everything it could to trace what happened after he left but had found "no evidence of him being alive".

Mr Levinson's family said it had learnt that he was dead but gave no information on how or when.

"We recently received information from US officials that has led both them and us to conclude that our wonderful husband and father died while in Iranian custody," a statement from the family said.

Mr Mousavi called on Washington to make an official announcement if Mr Levinson's death was confirmed, without "politicising and exploiting the family's feelings".

Iran's chief press officer at the United Nations Alireza Miryousefi had said earlier that Tehran had "no knowledge" of Mr Levinson's whereabouts.

The family said Mr Levinson died before the coronavirus pandemic, which has hit Iran hard and led authorities to release thousands of prisoners temporarily.

Mr Levinson is one of a number of Americans who have disappeared in arch-enemy Iran, but his case has been among the most perplexing, with his family until now insisting he was alive.

The father of seven vanished in March 2007 in Kish, an island that has more lenient visa rules than the rest of Iran, and was said to have been investigating cigarette counterfeiting.

But The Washington Post reported in 2013 that Mr Levinson, who had retired from the FBI, was working for the CIA and had gone on a rogue mission aimed at gathering intelligence on Iran.