This video purporting to show Mr Amiri was posted on YouTube
The Iranian government says it has evidence that one of its nuclear scientists was abducted and is being held in the US against his will.
Shahram Amiri disappeared a year ago while on a pilgrimage in Saudi Arabia.
Iranian television broadcast a video purporting to show the scientist saying he was kidnapped and is now living in Arizona.
It comes a day after another video, posted on YouTube, appeared to show Mr Amiri saying he was happy in the US.
Mr Amiri worked as a researcher at a university in Tehran, Ir anian media reported.
But other reports said he worked for the country's Atomic Energy Organisation and had in-depth knowledge of the country's nuclear programme.
'Drugged'
In the video shown on the Islamic Republic of Iran Broadcasting network, the man says he was forced to say he defected with a laptop full of evidence about Iran's nuclear secrets and that he was being used to put pressure on Iran.
The video showed a man wearing headphones and talking to his webcam.
He says he was in the Saudi city of Medina as part of a Muslim pilgrimage when Saudi intelligence officers drugged and kidnapped him.
"When I became conscious, I found myself in a plane on the way to the US," he was quoted as saying by Associated Press news agency.
"Since I was a bducted and brought to the US I was heavily tortured and pressured by US intelligence."
The man said the recording was made on 5 April in the city of Tucson, in Arizona.
'Free and safe'
In the video posted on YouTube, however, the man says he lives safely in the city and wants to continue his education in the US.
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I am Iranian and I have not taken any steps against my homeland
Shahram Amiri
YouTube broadcast
"I am free here and I assure everyone I am safe," he said in Farsi. The clip was posted on 7 June.
"My purpose in today's conversation is to put an end to all the rumour s that have been levelled at me over the past year. I am Iranian and I have not taken any steps against my homeland."
Neither the US nor the Saudi Arabian governments have made any comment on the allegations that he was abducted and taken to the US.
In March US news channel ABC ran a report that said Mr Amiri had defected and was helping the US compile intelligence on Iran's nuclear weapons programme.
The US and its allies believe Iran is trying to acquire a nuclear weapon, but Tehran denies the charge.
