Austrian officials have voiced their relief after two of the country's citizens were released by Iran after years of imprisonment in the country.

Dual Austrian-Iranian nationals Kamran Ghaderi and Massud Mossaheb were freed as part of a prisoner swap involving Europeans and an Iranian diplomat.

Belgium said a third person - a Danish citizen - had also been released.

The trio were flying into Belgium via Oman following medical examinations, Belgian Prime Minister Alexander De Croo said.

Local media reported that they will be met at the Melsbroek military airport just outside Brussels by Foreign Minister Hadja Lahbib.

Her Austrian counterpart, Alexander Schallenberg, tweeted his relief that both men could come home after years of "arduous imprisonment".

Ghaderi was arrested in Iran in 2016, and sentenced to ten years in jail on spying charges - after what his family says was a forced confession.

The pair spent 2,709 and 1,586 days in confinement respectively.

The earlier prisoner swap between Belgium and Iran involved Belgian aid worker Olivier Vandecasteele and Iranian diplomat Assadollah Assadi.

Mr Vandecasteele was freed after 455 days in prison, the Belgian prime minister said.

He ha been sentenced to 40 years in prison and 74 lashes in January, after being convicted of espionage and several other charges. He denied any wrongdoing.

Mr Assadi was convicted on terrorism charges in Belgium in 2021 in relation to a failed bomb plot in France, and had been jailed for 20 years.