The UN’s nuclear watchdog, the International Atomic Energy Agency (IAEA), says Tehran has fulfilled its side of last year’s landmark deal with six world powers.
“Iran has carried out all measures required under the (July deal) to enable Implementation Day (of the deal) to occur,” the Vienna-based agency said in a statement.
In return, the United States, European Union and United Nations have lifted a raft of nuclear-related sanctions.
The move will allow Iran to immediately recoup some $100bn (£70bn) in assets frozen overseas.
US Secretary of State John Kerry said: “I hereby confirm that the International Atomic Energy Agency has verified that Iran has fully implemented its required commitments… The US sanctions-related commitments… are now in effect.”
Meanwhile, in a joint press conference with Iran’s Foreign Minister Javad Zarif, EU foreign policy chief Federica Mogherini said: “As Iran has fulfilled its commitments, today multilateral and national economic and financial sanctions related to Iran’s nuclear programme”.
“(The deal’s) proper implementation will be a key contribution to improve regional and international peace, stability and security,” she said.
The announcement came hours after the US and Iran reached an agreement on a prisoner swap, bringing an end to 14 months of negotiations,
Tehran confirmed that four inmates with dual Iranian-US nationality have been released from its jails, including Washington Post reporter Jason Rezaian,
US officials say a fifth American, student Matthew Trevithnick, has also been freed, but that his release was not part of the prisoner swap.
Seven Iranians, being held in prisons across the US, have been released in return.
Western powers imposed sanctions on Iran over fears it was planning to use its atomic programme to develop nuclear weapons, although Tehran always maintained its nuclear ambitions were peaceful.
It is thought that since 2012 the sanctions have cost Iran on some £102bn in oil revenues alone.
Iran has the fourth biggest oil supplies in the world and the free flow of Iranian oil into the world market could mean lower prices at the pumps.
Restrictions on Iran’s shipping, energy, banking and automotive sectors will begin to be lifted, along with so-called secondary sanctions, which penalised foreign nationals with large dealings in Iran, being cancelled. Some sanctions not linked to the nuclear deal will, however, remain in place, including European sanctions relating to human rights and US sanctions relating to terrorism.
In comments posted on his official Twitter account, he wrote: “I thank God for this blessing & bow to the greatness of the patient nation of Iran. Congrats on this glorious victory!” Britain’s Foreign Secretary Phillip Hammond said it would make the world a “safer place.”
“The nuclear deal with Iran, in which Britain played a major role, makes the Middle East and the wider world a safer place,” Mr Hammond said in a statement.
“Years of patient and persistent diplomacy, and difficult technical work, have borne fruit as we now implement the deal,” he added.
There are those, however, who are alarmed at the prospect of closer western ties with Shiite Iran, chiefly Sunni Saudi Arabia and Israel.
According to Israeli Prime Minister Benjamin Netanyahu, Iran “has not relinquished its ambition to obtain nuclear weapons, and continues to act to destabilise the Middle East and spread terror throughout the world”.
The Iran deal with foreign powers operates on a snap-back system, meaning that sanctions would be re-introduced if Iran were deemed to violate the terms of the agreement in any way. Some of the deal’s provisions are also set to run out in 15 years, meaning that Iran could revert to enriching uranium to a higher level at a later stage.
“Iran may test the boundaries of the agreement. It is critical that violations do not go unpunished, or the deal could be killed by a thousand paper cuts,” Kelsey Davenport, of the Arms Control Association, said in a statement.
This year’s US presidential and congressional elections could also spell trouble for the deal, with many Republican presidential candidates likely to take a tougher stance on Iran. While many believe the deal will help boost the reformist camp in Iran, many conservatives have been less receptive to the new relationship with the West.