Last month, London changed its travel advice for British-Iranian dual nationals, warning them against all travel to Iran, citing Zaghari-Ratcliffe's case.
British woman held in Iran begins fresh hunger strike
A British-Iranian woman jailed in Tehran for more than three years has begun a hunger strike to protest her detention, her husband said Saturday.
Richard Ratcliffe said Nazanin Zaghari-Ratcliffe has told judicial officials she will refuse food but will drink water until she is granted "unconditional release".
"She has long been eligible for it," said Ratcliffe.
Zaghari-Ratcliffe previously went on hunger strike in January.
Ratcliffe said he would hold a vigil outside Iran's London embassy, and would fast in support of his wife.
Ratcliffe said his wife "had vowed that if we passed (daughter) Gabriella's fifth birthday with her still inside, then she would do something - to mark to both governments that enough is enough. This really has gone on too long".
Zaghari-Ratcliffe wrote an emotional letter to her five-year-old daughter to mark the occasion of her fifth birthday.
The letter, published by the Mirror, revealed that Zaghari-Ratcliffe's daughter Gabriella asked to celebrate her fifth birthday in prison with her mother.
Zaghari-Ratcliffe, who worked for the charity arm of news agency Thomson Reuters, was detained at Tehran airport in April 2016 as she was leaving Iran after taking her infant daughter to visit her family.
She was arrested on charges of plotting against the Iranian government. Her family denies the allegations.
Her daughter has resided with her maternal grandparents in Tehran since the arrest.
High-level diplomatic attempts to secure her release have so far failed. Foreign Secretary Jeremy Hunt granted 40-year-old Zaghari-Ratcliffe diplomatic protection in March, but Iranian officials refuse to recognize her dual nationality.
The hunger strike comes amid heightened tensions between the West and Iran, which the US and UK blame for attacks on two oil tankers in the Gulf of Oman this week. Iran denies involvement.
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