Iranian authorities have convicted an American-Iranian businessman on spying charges, US media has reported, in a recently revealed case which comes amid high tensions between the two countries.

The State Department confirmed late Monday in a statement to AFP that "we are aware of the reports that Iran has detained another US citizen".

It did not identify the person and declined to provide further details, but Iranian media on Thursday reported the conviction of Emad Sharqi, describing him as the deputy head for international affairs at an Iranian venture capital company called Sarava.

The Young Journalists Club, a news agency linked to Iranian state television, said Sharqi had been caught "trying to illegally flee the country from western borders". It did not disclose that he was a dual US citizen, as Tehran does not recognise bi-nationality. 

He had been sentenced to 10 years in prison on charges of espionage and gathering military information and was out on bail ahead of an appeal when he tried to abscond, the YJC said.

But a family friend quoted by NBC on Monday said Sharqi, 56, whom the US television channel identified as Iranian-American, was summoned to a Tehran court on November 30 and told that he had been convicted of espionage without a trial.

Revelations of the case come as US President-elect Joe Biden is due to be sworn in on Wednesday, with the difficult relationship between Washington and Tehran one of the top foreign policy challenges at the start of his administration.

Sharqi's case aside, three US citizens are known to be in detention in the Islamic republic.

The cases threaten to complicate potential engagement with Tehran on salvaging the Iran nuclear deal, a multilateral pact that has been on life support since 2018, when outgoing President Donald Trump unilaterally withdrew the US from the deal and began reimposing crippling sanctions on Tehran.    

NBC said that Sharqi was arrested in 2018, but was originally acquitted by an Iranian court in December 2019, ahead of his conviction late last year.