Five US citizens detained by Iran are now under house arrest, Washington and a lawyer for one of those imprisoned said.

The five Iranian-Americans had been in Tehran's Evin prison.

A lawyer representing one of those imprisoned said he hoped that this was the first step towards a prisoner swap.

A National Security Council spokesperson confirmed the transfer of five US citizens imprisoned in Iran to house arrest and said that negotiations for their release remained ongoing.

"While this is an encouraging step, these US citizens... should have never been detained in the first place," National Security Council spokesperson Adrienne Watson told reporters.

 "Of course, we will not rest until they are all back home in the United States," she added.

Who are the US citizens detained in Iran?

Those under house arrest include businessmen Siamak Namazi and Emad Shargi and environmentalist Morad Tahbaz, who is also a British citizen.

"The move by Iran of the American hostages from Evin Prison to an expected house arrest is an important development," Namazi's lawyer, Jared Genser, said in a statement.

"While I hope this will be the first step to their ultimate release, this is at best the beginning of the end and nothing more .... There are simply no guarantees about what happens from here," he said.

The fourth US citizen's identity has not been made public.

Namazi was detained in 2015 and later sentenced to 10 years in prison on spying charges. Tahbaz was arrested in 2018 for "assembly and collusion against Iran's national security" and also received a 10-year sentence.

Shargi was convicted of espionage in 2021 and sentence to 10 years.

Iran does not recognize dual citizenship.

House arrest first step in prisoner swap  — reports

The New York Times reported that the United States and Iran had reached a prison swap deal to release five US citizens, including Namazi, Shargi and Tahbaz.

Two names of the other two Americans were not disclosed.

In exchange for the release of its citizens, Washington had agreed to free several Iranians it had imprisoned for violating sanctions on Iran, according to the New York Times.

The US is also to transfer nearly $6 billion of Iran's assets in South Korea to an account in the central bank of Qatar, the paper said. The report said that the account is controlled by Qatar's government, with Tehran only being able to withdraw money for humanitarian purchases.

The Agence France-Presse (AFP) and Reuters news agencies cited unnamed sources that provided the same details of the deal.

Iranian state news agency IRNA confirmed the release.

"The Islamic Republic of Iran's mission at the United Nations confirmed the news of the release of dual-citizen prisoners from Tehran's Evin Prison,"  IRNA news agency reported. 

IRNA also cited Iran's mission to the US as saying that under a deal with Washington five Iranians jailed in the US will be freed.

Unnamed Iranian officials told the Associated Press that the prisoner transfer "marks a significant initial step in the implementation of this agreement."

Tehran has for months suggested that it could agree to a prisoner swap with the United States.

In March, the US called remarks by Iranian Foreign Minister Hossein Amirabdollahian, who claimed the two countries were close to reaching a deal, a "cruel lie."

sdi/wmr (Reuters, AP, AFP)