The husband of a British-Iranian woman detained in Iran on Wednesday led a protest in London demanding the release of his wife and another British citizen held in the Middle Eastern state.
Nazanin Zaghari-Ratcliffe, a 38-year-old mother, had already been sentenced to five years in prison for participating in anti-regime demonstrations in 2009, and last week was hit with further charges, carrying a possible 16-year prison term.
"We were very surprised," husband Richard Ratcliffe said of the new charges.
"We had been getting some positive noises in the past few weeks, she has been told she would be temporarily released and would just stay at home until she is allowed to come back to the UK," he said at the protest attended by around 50 Amnesty activists.
His wife was "very shocked" by the decision, which left her family "devastated," he added.
British Foreign Secretary Boris Johnson on Tuesday tweeted that he had held talks with Vice President of Iran Ali Akbar Salehi, where he had "underlined serious concern for dual national detainees" including Zaghari-Ratcliffe.
Her original five-year sentence was upheld on appeal in April and she now faces a further 16 years behind bars.
"These charges are linked to her work at BBC Media Action and at the Thomson Reuters Foundation," said Thomson Reuters Foundation director Monique Villa.
"The accusation states that her charity work was a screen to overthrow the Iranian regime," she added.
"This is a complete invention as the Thomson Reuters Foundation doesn't work in Iran and has no programme or dealings with Iran."
Ms Zaghari-Ratcliffe was arrested at Tehran's airport on April 3, 2016, after visiting her family in Iran with daughter, Gabriella, who was born in Britain and is now three-years old.
After being held in solitary confinement, she was transferred to the women's quarters of Evin Prison in Tehran on December 26.
She has since been visited by her daughter, whose British passport was confiscated and who is now living with her grandparents in Iran.
The protesters also demanded the release of detainee Kamal Foroughi, 78, who has been held since 2011 and is currently serving a seven-year term after being convicted on espionage charges.
"We have been lobbying the UK government to do more," for both detainees, Kathy Voss, a campaigner for Amnesty International, said.
"At the moment they have expressed their concerns. But they have to say publicly that they should be released," she added.