(CNN) - Abbas Edalat, a British-Iranian professor who was arrested and detained in Iran for eight months, has returned to the UK, according to British authorities.
"We can confirm that a British-Iranian dual national who was detained in Tehran has returned to the UK," a UK Foreign Office representative told CNN on Wednesday. "We continue to take action on all our consular cases in Iran in line with what we believe will produce the best outcomes in their cases."
Iranian security forces arrested Edalat in April on security charges after he was accused of being part of a British-affiliated, anti-Iran group that allegedly launched espionage operations and had contacts with leaders of mass anti-government protests in 2009, according to Iran's semiofficial Fars news agency.
No further details on the charges were given, and the group that Edalat was accused of being affiliated with was not identified.
Edalat, an award-winning Imperial College London professor of computer science and mathematics, is a prominent activist who founded the Campaign Against Sanctions and Military Intervention in Iran in 2005.
In a statement, that group described Edalat's detention as a "misunderstanding" on the part of Iranian officials.
"Professor Abbas Edalat, the founder of CASMII, returned to the UK this week. It increasingly appears, as we had suspected, that his detention in spring in Iran was a case of misinformation and misunderstanding by the Iranian security apparatus," the statement said.
On Monday, the New York-based Center for Human Rights in Iran issued an open letter alongside six families affected by the detention of dual and foreign nationals in Iran, highlighting the cases of at least 10 dual and foreign nationals who have been imprisoned without due process.
Among them are Ahmadreza Djalali, a Swedish-Iranian scientist facing a death sentence, and Robert Levinson, a US citizen and former FBI agent whom US investigators believe is being held there.
"We urge all our governments, especially those who enjoy diplomatic relations with the country of Iran, to acknowledge this hostage-taking crisis immediately and to take concrete steps that would help resolve these cases," the letter said.
Edalat's release comes as Nazanin Zaghari-Ratcliffe, a British-Iranian woman who has been imprisoned in Tehran since 2016, was preparing to mark a milestone birthday behind bars.
Zaghari-Ratcliffe, a project manager at the Thomson Reuters Foundation, was accused of spying and spreading propaganda against the regime.
UK Foreign Secretary Jeremy Hunt sent his wishes to Zaghari-Ratcliffe on Wednesday.
"Happy 40th Birthday Nazanin! Thinking of you & your family this Boxing Day," Hunt said on Twitter.
"If the thoughts and prayers of a whole nation can make a difference to you & other innocent people detained in Iran then this will be last birthday you will be suffering such a great injustice," he added.
On Christmas Day, Hunt asked the public not to forget about Zaghari-Ratcliffe and others in her position.
"As we celebrate, let's also remember those unjustly imprisoned like Nazanin Zaghari-Ratcliffe who is 40 tomorrow and separated from her brave husband Richard and devoted daughter Gabriella. Many more like her - we will not forget them today," he said.
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