Four environmentalists who spent more than five years in prison after being convicted of spying will be freed following a pardon from Iran's supreme leader, state media reported on Sunday.

Ayatollah Ali Khamenei has pardoned more than 2,000 inmates to mark celebrations for the end of the Muslim holy month of Ramadan.

Their release date was not immediately clear, but their lawyer Hojat Kermani said it would be "in the coming days".

"My clients were informed by the judiciary's deputy of human rights that they are included in the amnesty," Kermani told the official IRNA news agency.

He named his clients as Sepideh Kashani, Niloufar Bayani, Houman Jowkar, and Taher Ghadirain.

They were arrested in 2018 on suspicion of espionage for foreign governments, among other charges, and were given jail sentences of up to 10 years.

The environmentalists worked for Persian Wildlife Heritage Foundation, a conservationist organisation that protects endangered species.

In early 2018, Iranian-Canadian environmentalist and university professor Kavous Seyed Emami, 63, died in prison.

He reportedly committed suicide a fortnight after his arrest, an allegation rejected by his relatives.

In 2023, wildlife conservationist Morad Tahbaz was among five American prisoners released from Iran as part of a prisoner swap deal with the United States.