An environmentalist holding British and American citizenship has been released on bail by Iranian authorities, according to his lawyer.

Hojjat Kermani told the Emtedad and ILNA news websites on Wednesday that 66-year-old Morad Tahbaz, who also holds Iranian citizenship, was released with an ankle bracelet, without providing further information.

Tahbaz was arrested in January 2018 on security charges alongside seven other environmentalists, and was sentenced to 10 years in prison in November 2019.

In March, there was speculation that he would be released from prison and flown out of the country along with two other British-Iranian dual nationals.

At the time, the British government struck a deal with the Iranian authorities for the release of 43-year-old Nazanin Zaghari-Ratcliffe and 67-year-old Anoosheh Ansari.

Their release came shortly after years of negotiations led to the British government repaying a debt of 400 million pounds it owed Iran from before the country’s 1979 revolution.

The British government had claimed in March that Tahbaz was also included in the deal that secured the other two prisoners’ release, but he was never released.

“It is a very very difficult situation. Morad Tahbaz is a tri-national. We pushed very hard to get Morad out of prison,” the United Kingdom’s foreign minister, Liz Truss, had said in the British parliament about his case at the time.

Tahbaz’s sister had accused the British government of abandoning him at the time.

“He continues to be used as a pawn on a chessboard. And it’s very distressing, we’re agonising, we’re absolutely distraught, and we don’t know what the next moves are,” Tarane Tahbaz said in March.

Tahbaz went on a hunger strike in protest against his continued imprisonment, but later broke it due to health concerns. He is reportedly a cancer survivor and has contracted COVID-19 twice in the past.

Tahbaz, who was born in London, has denied charges that he was gathering information for foreign powers under the guise of environmental work.

Iran has been accused of using prisoners holding Western passports as bargaining chips, a charge Iran denies.