The news agency Mizan reported Tuesday that guilty verdicts had been handed down to business consultant Siamak Namazi and his father Baqer Namazi, a former UNICEF official.

"Baquer and Siamak Namazi... have been sentenced to 10 years in prison for espionage and collaboration with the American government," prosecutor-general Abbas Jafari Dolat-Abadi said, according to the Fars news agency

Video footage of Namazi's arrest was published by Mizan - closely linked to the judiciary - this week, alongside images of his US passport and shots of "Washington Post" journalist Jason Rezaian. The reporter spent two years in prison on espionage charges and was released in January as a nuclear accord came into force and sanctions were lifted on Iran.

Mizan published a long article in February, criticising the Namazi family's efforts to "influence internal events in Iran" through its financial contributions to NGOs.

Iranian authorities said that they had video material showing the two men involved in a spy operation. Conservative Iranian media have criticised Siamak Namazi's links to the National Iranian American Council, a Washington-based NGO created by Iranian nationals.

Siamak Namazi, a well-connected business consultant who has supported reformist politicians in Iran, was arrested as he arrived in Tehran a year ago.

At the time of his arrest last year, he was working for Crescent Petroleum, an energy firm based in the United Arab Emirates, which is involved in an ongoing legal dispute with Iran over a failed gas deal, and is seeking billions of dollars in compensation. His father, Baquer, was detained in February when he came to Iran to seek his son's release.

Concerned voices

UNICEF, with which Baqer Namazi had previously worked as a representative to Somalia, Kenya and Egypt, noted the sentence with "sadness and personal concern," said Stephane Dujarric, spokesman for UN Secretary General Ban Ki-moon.

"He deserves a peaceful retirement and UNICEF appeals for his release on humanitarian grounds," Dujarric said.

The US was also "deeply concerned" about the sentencing noting that the two men had been "unjustly detained," said Mark Toner, a spokesman for the US State Department.

"We join recent calls by international organizations and UN human rights experts for the immediate release of all US citizens unjustly detained in Iran, including Siamak and Baquer Namazi, so that they can return to their families," Toner said.

The US also expressed concerns about reporters of the "declining health" of Baquer Namazi.

In its statement, the State Department also raised the case of Robert Levinson (pictured above), a former FBI agent and ex-CIA contractor who went missing on Iran's Kish Island in 2007.

jbh/jr (AFP, dpa)