Questions surrounded the death of a prominent Iranian-Canadian environmentalist on Sunday after authorities claimed he committed suicide in prison after his arrest.

Iran's academic community was in shock over the death of Kavous Seyed Emami, 63, one of the country's most revered professors and head of the Persian Wildlife Heritage Foundation.

He was arrested along with seven colleagues from the wildlife NGO on January 24, and his death was announced by the family on social media late on Saturday.

There were also unconfirmed reports that the deputy head of Iran's Department of Environment, Kaveh Madani, had been arrested.

"The news of my father's passing is impossible to fathom," wrote Emami's son Ramin Seyed Emami, a well-known singer, on his Instagram page.

He said security officials had informed his mother on Friday.

"They say he committed suicide. I still can't believe this."

A reformist lawmaker, Mahmoud Sadeghi, wrote on Twitter that he phoned the Environment Protection Organisation to find out about the case and was told that its deputy head, Madani, had also been arrested on Saturday.

Madani, 36, was an award-winning academic working at Imperial College London, well-known for his activism on water conservation, when he was appointed by the government in September.

His arrest could not be immediately confirmed by AFP.

Asked about Emami's case on Sunday, Tehran's chief prosecutor Abbas Jafari Dolatabadi confirmed the death.

"This person was one of the accused and given that he knew there were many revelations against him and that he himself had made confessions, unfortunately he committed suicide in prison," he told the reformist ILNA news agency.

Dolatabadi had said on Saturday that several people linked to environmental causes had been arrested on espionage charges, without giving further details.

- Multiple 'suicides' -

The Iran Sociology Association, of which Emami was an active member, released a statement questioning the claims.

"The information published about him is not believable and we expect officials to respond and to provide the public with information concerning his death," the statement said.

A source close to the Persian Wildlife Heritage Foundation told AFP that the other seven were still in jail.

Among them was Hooman Jokar, who headed a programme to save the endangered Asiatic cheetah.

This handout photograph released on February 11, 2018 by the family of Iranian-Canadian environmentalist Kavous Seyed Emami shows him at an unidentified location HANDOUT, FAMILY HANDOUT/AFP

Morad Tahbaz, an Iranian-American businessman who was a member of the Persian Wildlife Heritage Foundation board, was also in detention.

Iran does not recognise dual nationals and treats them purely as Iranians, denying them certain consular services.

In November, the conservative-linked Tasnim news agency accused Tahbaz of being a big-game hunter who was trying to seize control of national park land in northern Iran.

Tahbaz comes from a wealthy family who made their fortune before the 1979 revolution and once owned the renowned Kayhan newspaper, which is now controlled by the Islamic authorities.

Emami's death follows reports of at least two other "suicides" in detention that were linked to protests in late December and early January.

Mahmoud Sadeghi, an outspoken lawmaker, had claimed a 23-year-old protester named Sina Ghanbari died in Tehran's notorious Evin Prison, but the judiciary said he was a drug-trafficker who had committed suicide.

Another man died after being arrested during protests in the city of Arak in central Iran. Local officials said he had stabbed himself to death.

- 'Loved Iran, the environment' -

"Everyone is in shock," an academic who knew Emami well told AFP on condition of anonymity.

"He was one of the best professors. He was very profound, very composed, not at all political. He loved Iran and the environment.

"He came back recently from Canada where he was doing research. On his return, he was called in several times" by the authorities.

A spokesperson for Canada's Global Affairs, which deals with its external relations, said they were aware of the reports.

"Canadian consular officials in Ankara are working to gather additional information and are providing information and assistance to the family," she said.

Canada's Ankara embassy deals with Iranian affairs since the country severed diplomatic relations with Iran in 2012 over its support for the Syrian regime, "incitement to genocide" against Israel and its leaders' failure to account for their nuclear programme.

Emami is the second Iranian-Canadian citizen to die in Iran's prisons following the murder of 54-year-old Zahra Kazemi in 2003, who had been arrested for taking photos outside Evin Prison.

Iranian-Canadian environmentalist Kavous Seyed Emami, who authorities say died in prison, headed the Persian Wildlife Heritage Foundation which worked to preserve rare species like the Asiatic Cheetah ATTA KENARE, AFP

The vice-president at the time, Mohammad Ali Abtahi, stated she died from "a brain haemorrhage caused by a beating".

After a landmark nuclear deal between Iran and world powers in 2015, Canada announced the lifting of economic sanctions on the country and said it was reviewing its wider relations.