Pakistan has confirmed a missing Iranian nuclear scientist, who Tehran says was kidnapped by the CIA, has taken refuge in the Iranian section of its embassy in Washington.

Pakistan's embassy handles Iran's interests in the US because the two countries have had no diplomatic relations for three decades.

Shahram Amiri went to the Iranian Interest section at the Pakistani Embassy in Washington yesterday and asked to be returned to Tehran.

Last week Iran submitted a dossier, of what it said was evidence of the scientist's kidnapping by US agents in 2009, to the Swiss embassy in Tehran.

In recent months three videos purporting to be Amiri have surfaced, the first claiming he had been kidnapped, the second claiming he was living freely in Arizona and the third claiming he has escaped from his captors.

US officials at the time described the claims as ludicrous.