berlin - Iran has released one Danish and two Austrian citizens, the European countries said Friday, thanking Oman and Belgium for their help in getting the trio freed.

Austrian Foreign Minister Alexander Schallenberg said he was 'very relieved' that Kamran Ghaderi and Massud Mossaheb were being brought home after 'years of arduous imprisonment in Iran.'

Denmark's foreign minister, Lars Løkke Rasmussen, said that he was 'happy and relieved that a Danish citizen is on his way home to his family in Denmark after imprisonment in Iran.' He didn't name the person, saying their identity was 'a personal matter' and he couldn't go into details.

Schallenberg thanked the foreign ministers of Belgium and Oman for providing 'valuable support,' without elaborating on what form it took. Løkke Rasmussen also thanked Belgium and said that Oman 'played an important role.'

Last week, a prisoner exchange between Belgium and Iran returned to Tehran an Iranian diplomat convicted of attempting to bomb exiles in France, Assadollah Assadi. Belgian aid worker Olivier Vandecasteele, looking visibly gaunt, headed back to Brussels as part of the swap.

FILE - Belgium's Olivier Vandecasteele, left, is greeted by his family after landing at Melsbroek military airport in Melsbroek, Belgium, May 26, 2023. He was detained in Iran for nearly 15 months.

There was no immediate word on what, if anything, Iran obtained in return for the latest releases.

On Friday, Belgian Foreign Minister Hadja Lahbib tweeted that her country was 'unwavering in our dedication to advocating for other Europeans who are being arbitrarily detained' and had 'successfully secured the release of two Austrians and one Dane who were unjustly held in detention in Iran.'

Belgium's prime minister, Alexander De Croo, said he had briefed his Austrian and Danish counterparts at a Thursday meeting in Moldova on the 'imminent release' of the three prisoners 'heading to Belgium via Oman.'

Iranian state media and officials did not immediately acknowledge a release on Friday, which is part of the weekend in the Islamic Republic.

Oman often serves an interlocutor between Iran and the West and brings released captives out of the Islamic Republic. An Oman Royal Air Force Gulfstream IV, which had been on the ground in Tehran for several days, took off shortly before news of the European trio's releases came out. It landed later Friday in Oman's capital, Muscat.

The releases also come after Oman's Sultan Haitham bin Tariq visited Iran on his first trip there since becoming the Arab nation's ruler in 2020.

Ghaderi is an Iranian-Austrian businessman who was arrested in 2016 and later sentenced to 10 years in prison for allegedly spying for the U.S., charges strongly rejected by his supporters. His family had criticized Austria for being silent on his case in recent years.

Mossaheb, also an Iranian-Austrian businessman, was arrested in 2019 and received a 10-year prison sentence after what Amnesty International called 'a grossly unfair trial for vague national security offenses.' Amnesty had said Mossaheb suffered from heart failure and diabetes, making his imprisonment much more dangerous for him.

Iran has detained a number of foreigners and dual nationals over the years, accusing them of espionage or other state security offenses and sentencing them following secretive trials in which rights groups say they have been denied due process.

Critics have repeatedly accused Iran of using such prisoners as bargaining chips with the West.

Schallenberg said his ministry would spare no effort to secure the release of a third Austrian national who remains in detention in Iran and whose case is currently on appeal.