Iran has arrested three more environmentalists on spying charges, the country's powerful judiciary has said.

The arrests on February 25 came weeks after a wave of detentions and the death of a well-known Iranian-Canadian environmentalist who died in Iranian custody.

Judiciary spokesman Gholamhossein Mohseni Ejei, quoted by the semi-official Fars news agency, said on February 25 that three people were recently arrested in the southern province of Hormozgan.

"There is no doubt that infiltration by the United States and Israel is a serious matter," the spokesman said, without offering further details on the arrests.

Iranian officials have said the activists who have been arrested were gathering sensitive information under the guise of scientific and environmental activities on behalf of the CIA and Israel's Mossad.

The arrests come after the death of Kavous Seyed-Emami, the Iranian-Canadian managing director of the Persian Wildlife Heritage Foundation and a lecturer in sociology in Tehran, who was arrested on January 24 and died in prison two weeks later.

The judiciary said Seyed-Emami, 63, had committed suicide.

The Center for Human Rights in Iran (CHRI), a non-profit organization based in New York, said at least nine other members of Seyed-Emami's organization had been arrested on the same day as him.

Seyed-Emami's death along with other inmate "suicides" have sparked a government probe and fueled tension between Iran's dominant hard-line institutions and its president, a relative moderate.

Former Intelligence Minister Ali Yunesi, an advisor to Rohani, criticized the handling of Seyed-Emami's case and suggested the public did not believe the official explanation for his death.

"Given the events that have occurred, if a competent and legal agency does not intervene and doesn't give its opinion on the dead individual or those under arrest, public opinion will not believe they are spies even if they are convicted," he said in an interview with the daily Iran newspaper published on February 25.

Yunesi, who was a minister under reformist President Mohammad Khatami, said the case should be handed to the Intelligence Ministry.

Seyed-Emami's case is said to have been handled by Iran's powerful Islamic Revolutionary Guards Corps (IRGC), which runs an intelligence service that is separate from the government's Intelligence Ministry.

Human rights activists have reported that at least six detainees have died in prisons in the last two months in Iran. The judiciary has confirmed three deaths in custody but said all three were suicides.

With reporting by Fars and Reuters