The suspect was a trainee in the Iranian year beginning in March 2014 and "dismissed the same year due to moral issues and addiction", the armed forces general staff said in a statement carried by the IRNA state news agency.

The individual had "never been officially recruited" and as a civilian "would fall under the jurisdiction of the intelligence ministry" for monitoring, it said, in a rare public row between a security service and the military in the Islamic republic.

Top nuclear scientist Mohsen Fakhrizadeh was travelling on a highway outside Tehran accompanied by a security detail on November 27 when he came under machine-gun fire, according to Iranian authorities.

Intelligence Minister Mahmoud Alavi said in an interview with state television on February 8 that a member of the armed forces "carried out the first preparations" for the killing, and that it was not possible for his ministry "to keep watch over the armed forces".

In response, the armed forces said it expected Alavi "to be more careful in his remarks to the media" so as not to serve the interests of Iran's enemies and safeguard "the dignity of the armed forces" and his ministry.

On Sunday, the minister was quoted by ISNA news agency as saying the suspect was an "ex-member of the armed forces" and had left Iran before the assassination.

According to Iranian authorities, Fakhrizadeh was a deputy defence minister and carried out work on "nuclear defence".

Iran's Revolutionary Guards said a satellite-controlled gun with "artificial intelligence" was used in the attack, which Tehran blamed on its arch foe Israel.

The Jewish state did not react to the accusation but Israeli Prime Minister Benjamin Netanyahu said in 2018 that Fakhrizadeh headed a secret nuclear arms programme, whose existence Iran has repeatedly denied.