The husband of a British-Iranian woman jailed in Tehran for over three years says she has begun a hunger strike to protest her detention.

Richard Ratcliffe said Saturday that Nazanin Zaghari-Ratcliffe told judicial officials she will refuse food but will drink water until she is granted "unconditional release."

Ratcliffe said he would hold a vigil outside Iran's London embassy, and would fast in support of his wife.

Zaghari-Ratcliffe, who worked for the charity arm of news agency Thomson Reuters, was arrested in April 2016 on charges of plotting against the Iranian government. Her family denies the allegations.

The hunger strike comes amid heightened tensions between the West and Iran, which the U.S. and U.K. blame for attacks on two oil tankers in the Gulf of Oman this week. Iran denies involvement.