Five US citizens left Iran and landed in Doha in a prisoner swap for five Iranians held in the United States and the transfer of $6 billion in Iranian funds in a rare deal between the long-time antagonists.
"Today, five innocent Americans who were imprisoned in Iran are finally coming home," US President Joe Biden said in a statement on Monday, adding they "will soon be reunited with their loved ones — after enduring years of agony, uncertainty, and suffering."
It was unclear whether the exchange might bring progress on the many issues that divide the two nations, including Iran's nuclear programme, its support for regional Shia militias, the presence of US troops in the Gulf and US sanctions on Iran.
A plane sent by mediator Qatar flew the five U.S. citizens and two of their relatives out of Tehran after both sides got confirmation the funds had been transferred to accounts in Doha, a source briefed on the matter told Reuters.
A Reuters witness saw the plane land at Doha International Airport.
US officials received the five Americans after they disembarked from the Qatari plane at Doha, the Reuters witness said. Switzerland's ambassador to Iran accompanied them on the plane to Doha, the witness added.
Earlier, two of the five Iranians landed in Qatar, a US official said. Three have opted not to return to Iran.
The five Iranian Americans - one of whom had been held for about eight years on charges the United States had rejected as baseless - were due to board a US government aircraft in Doha and then fly home to the United States.
The deal, after months of talks in Qatar, removes a major irritant between the US, which brands Tehran a sponsor of terrorism, and Iran, which calls Washington the "Great Satan".
A senior US administration official said the deal did not change Washington's adversarial relationship with Tehran, but the door was open for diplomacy on Iran's nuclear programme.
Qatar, a tiny but hugely wealthy Gulf Arab energy producer, has sought to raise its global profile, hosting the soccer World Cup last year and carving out a role in international diplomacy.
Doha hosted at least eight rounds of talks with Iranian and US negotiators sitting in separate hotels, speaking via shuttle diplomacy, a source previously told Reuters.
The transfer of Iran's funds under the agreement has drawn criticism from US Republicans who say President Joe Biden, a Democrat, is in effect, paying a ransom for US citizens.
The White House has defended the deal.