A British-Iranian woman jailed in Tehran for more than three years has begun a new hunger strike to protest against her detention, her husband announced on Saturday.

Speaking outside the Iranian Embassy in London, Richard Ratcliffe said Nazanin Zaghari-Ratcliffe had told judicial officials in June she would refuse food but would drink water until she was granted unconditional release.

Zaghari-Ratcliffe, who worked for the charity arm of news agency Thomson Reuters, was detained at Tehran airport in April 2016 on charges of plotting against the Iranian government. She was convicted of spying and sentenced to serve five years in Tehran’s Evin Prison.

She and her family have denied the allegations.

Ratcliffe said he would hold a vigil outside the embassy, and would fast in support of his wife, who previously went on a hunger strike in January.

On a petition website dedicated to freeing his wife, Ratcliffe said she has “long been eligible” for an unconditional release.

The detainee’s husband, Richard Ratcliffe, appears during an Amnesty International-led vigil outside the Iranian Embassy in London on Jan. 16, 2017. (Alastair Grant/Associated Press)

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.

Reacting to the news that she had begun a hunger strike, Hunt on Saturday sent a message to Iran via Twitter, urging the Iranian government to “do the right thing, show the world your humanity & let this innocent woman home.”