Iran has released a detained US military veteran from custody due to unspecified medical reasons under the condition that he remains in the country, State Department Secretary Mike Pompeo said in a statement on Thursday.

Michael White, a US Navy veteran, had been held in the country since 2018 before he was released this week on medical furlough. In a statement, Mr Pompeo said the veteran had been “wrongfully detained by the Iranian regime” as he served a 13-year prison sentence.

“His release on humanitarian grounds was conditioned upon him staying in Iran”, the secretary of state said.

Mr White reportedly has reportedly been diagnosed with cancer. He was moved to the Swiss embassy in Iran this week, according to officials, where he has been receiving treatment.

The State Department also said on Thursday that the agency “will continue to work for Michael’s full release”.

Mr Pompeo thanked Switzerland for “its continued and constructive role as our protecting power in Iran” while calling on Tehran to release the following additional prisoners on humanitarian grounds: Morad Tabbaz, Baquer Namazi and Siamak Namazi.

The 47-year-old was reportedly pursuing a romantic relationship with an Iranian woman in the northeastern city of Mashhad when he was arrested by Iranian security forces in July of last year.

His family members previously revealed he suffered from cancer in an interview with the New York Times, adding: “We think that Michael is in really poor health.”

They added: “Under no circumstances do we think the Iranians are providing him with adequate care.”