Five U.S. detainees flew out of Iran on Monday in a swap for five Iranians held in the U.S. under a rare deal brokered by Qatar between the arch enemies that also unfroze $6 billion of Tehran's funds.

A Qatari plane took off from Tehran carrying the five with two of their relatives, shortly after the U.S. and Iran received confirmation that the funds had been transferred to accounts in Doha, a source briefed on the matter told Reuters.

Iran's Press TV said two of the five Iranians to be released in the exchange had landed in Doha. There was no independent confirmation, though Iranian officials had said three of those to be freed by the U.S. were not returning to Iran.

The funds' release triggered an exchange sequence agreed after months of talks between the United States and Iran, who are at odds over Tehran's nuclear ambitions and other issues.

The five Americans with dual nationality are due to fly to Doha and then on to the U.S. "They are in good health," an Iranian official briefed on the process said.

Iran's Foreign ministry spokesperson Nasser Kanaani said two of the Iranians being released would return to Iran while two would stay in the U.S. at their request. One detainee would join his family in a third country, he added.

Kanaani said the funds, blocked in South Korea after U.S. sanctions on Iran were hardened in 2018, would be available to Tehran on Monday. Under the deal, Qatar will ensure the cash is spent on humanitarian goods and not items under U.S. sanctions.

The deal will remove a major irritant between the U.S., which brands Tehran a state sponsor of terrorism, and Iran, which calls Washington the "Great Satan."

But they remain deeply divided on other issues ranging from Iran's nuclear program and its influence around the region to U.S. sanctions and America's military presence in the Gulf.

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. The Sunni Muslim nation hosts a big U.S. military base but has also forged close ties with Shiite Muslim Iran.

(Cover: Iran's delegation, front left, and the US delegation, front row rear, rise as judges take their seats at the International Court of Justice, the United Nations' top court, which issued its judgment in a dispute between Iran and the United States over frozen Iranian state bank accounts worth some $2 billion, in The Hague, Netherlands, March 30, 2023. /CFP)