Canada on Tuesday stepped up its demand for answers after the death of renowned Iranian-Canadian environmentalist Kavous Seyed Emami, who Iranian officials say committed suicide in prison.
Tehran's chief prosecutor accused Emami of being part of an espionage network set up by Israel's Mossad and the CIA.
"We are seriously concerned by the situation surrounding the detention and death of Mr Seyed Emami," Minister of Foreign Affairs Chrystia Freeland said in a statement, adding Ottawa has "repeatedly" expressed concerns over the case.
"A Canadian has died. We expect the Government of Iran to provide information and answers into the circumstances surrounding this tragedy," she said.
Freeland pledged "to use every means at Canada's disposal to seek further information."
Emami, 63, a professor and founder of the Persian Wildlife Heritage Foundation, was buried on Tuesday in the village of Ammami around 40 kilometers (25 miles) north of the capital Tehran.
Iranian officials say he committed suicide in his prison cell a fortnight after being arrested along with seven members of his non-governmental organization.
Tehran prosecutor Abbas Jafari Dolatabadi said on Tuesday the NGO was set up "about a decade ago" as a cover to collect "classified information in defense and missile fields."
He said Emami was one of the main contacts for US agents and an intelligence officer had stayed at his home.
A post-mortem was carried out on Emami's body on Monday after family and colleagues raised doubts about his suicide.
Payam Derafshan, a lawyer for the family, told the ILNA news agency that he had watched a video from the cell along with the family, which authorities have said proves he killed himself.
"Because there is not a good angle... the act of suicide is not clear," Derafshan told ILNA.
On Monday, Omar Alghabra, Canada's parliamentary secretary to the minister of foreign affairs, expressed Canada's concern about the Emami case and said Ottawa "has asked Iranian authorities for answers."