EU foreign policy chief Federica Mogherini attends a press conference in Vienna, Austria, Jan 16, 2016. [Photo/Xinhua]

Mogherini said the implementation day marks the key fact that diplomacy could resolve tough issue.

Meanwhile, US Secretary of State John Kerry told reporters the world is safer as Iran is barred from nuclear weapon, as all the paths to the bomb are blocked by the deal, Tehran could only use the atomic energy for peaceful purpose, adding that Iran needs to be also compliant to their commitment in the coming years.

The EU lifted its economic sanctions against Iran after the UN nuclear watchdog's announcement.

"As Iran has fulfilled its commitments, today, multilateral and national economic and financial sanctions related to Iran's nuclear program are lifted," Mogherini said.

Shortly after the IAEA announcement, US President Barack Obama on Saturday also signed an executive order to lift sanctions on Iran related to its nuclear program, the White House said.

Meanwhile on another development, Kerry noted the five American prisoners are freed by Tehran and are on their way back to the United States.

Iranian media reported one of the Americans freed is a Washington post reporter, while US releases seven Iranian nationals serving jail terms in a prisoner swap with Tehran.