Iran said Tuesday it will use legal channels to secure the release of its nuclear scientist Shahram Amiri, who in a video clip screened on Iranian television channels said he was kidnapped by US agents.

Foreign ministry spokesman Ramin Mehmanparast said the film confirmed Tehran's charges that Amiri had been "kidnapped by US and Saudi intelligence services."

But Washington denied the accusation.

"Have we kidnapped an Iranian scientist? The answer is no," State Department spokesman Philip Crowley said in Washington.

In the clip aired Monday, the man identified by Iranian state television as Amiri said he was now "in the city of Tucson, Arizona" in the United States and that he had been kidnapped by US agents en route to Mecca in Saudi Arabia in June 2009.

Amiri stated that his abduction was intended to mount political pressure on the Iranian government.

The television said Iranian intelligence services had obtained the film "by special methods," without elaborating.

"These are inhumane actions and violate international laws," Mehmanparast said at his weekly press conference broadcast live on Iran's English-language channel Press TV.

"We won't allow this to happen to our nationals and through legal channels we will pursue the issue."

Later on Tuesday, Tehran summoned the ambassador of Switzerland, which represents Washington's interests in Iran in the absence of a US embassy, the official IRNA news agency reported.

"The US is responsible for the safety of Mr Amiri," foreign ministry official Ali Akbar Rezai was quoted as telling the Swiss envoy, Livia Leu Agosti.

"The abduction of an Iranian citizen is contrary to the international law, human rights and international obligations assumed by the United States of America," Rezai added.

He called for the "immediate release and unconditional return of Mr Amiri to the Islamic republic of Iran," IRNA said.

The report added that documents "confirming the abduction of Shahram Amiri along with a protest letter" were handed to the Swiss envoy.

The man in the footage is filmed in a closed room, apparently with the use of a webcam, and wearing headphones.

He said he was "taken to a house somewhere in Saudi Arabia ... They gave me an injection and when I woke up I was on a plane headed for the US," where he was being "subjected to the worst torture and moral pressure" by his guards.

"Their aim is to make me give an interview to one of the major US television networks to say I'm an important figure in the Iranian nuclear programme and that I have asked for asylum in the United States," he said.

"I have to say that I have important documents in my possession as well as a computer with secret information," the man said, asking for human rights organisations to press for his release.

ABC news in the United States reported in March that Amiri, a nuclear physicist in his early 30s who disappeared in June 2009 after arriving in Saudi Arabia on a pilgrimage, had defected and was working with the CIA.

Iranian officials have long maintained that Amiri was abducted from Saudi Arabia by US agents while on pilgrimage to the Muslim holy places.

The ABC report said that US agents described the defection as "an intelligence coup" in efforts to undermine Iran's controversial nuclear programme.

Amiri's disappearance "was part of a long-planned CIA operation to get him to defect," ABC reported.

The Islamic republic is demanding the release and repatriation of Amiri along with 10 other Iranian nationals who it says have been "illegally detained" in the United States.

In May, Intelligence Minister Heydar Moslehi linked the case of Iranians held in the United States to that of three US hikers detained in July 2009 for illegal entry into Iran from neighbouring northern Iraq.

But Mehmanparast said the two issues were not linked.

"We have no agenda for exchange when it comes to people who have an open judicial case. The three Americans entered Iran illegally and an investigation is ongoing," he said.

Shane Bauer, Josh Fattal and Sarah Shourd are being held in Tehran and their mothers visited them last month.

In the absence of diplomatic relations between Tehran and Washington, US interests are represented by the Swiss embassy in Iran, while the Islamic republic's interests are represented by the Pakistani mission in Washington.