Hassan Firuzabadi, senior military advisor to Iran's Supreme Leader Ayatollah Ali Khamenei and former chief of staff of the country's armed forces, has said he believes that Western spies have used lizards to spy on Iran's nuclear programme.

He was taking questions from local media following the death of an Iranian-Canadian environmentalist in prison. The man in question, Kavous Seyed Emami, was arrested last month with several members of his wildlife NGO.

Firuzabadi said he did not know details of the case, but claimed that the West had often used people posing as tourists and scientists to spy on Iran.

"Several years ago, some individuals came to Iran to collect aid for Palestine... We were suspicious of the route they chose," Firuzabadi told ILNA news agency (via Middle East Eye).

"In their possessions were a variety of reptile desert species like lizards, chameleons... We found out that their skin attracts atomic waves and that they were nuclear spies who wanted to find out where inside the Islamic Republic of Iran we have uranium mines and where we are engaged in atomic activities," he said.

He added that Western spy agencies have "failed every time" before describing another case involving a couple from Germany.

"They got them on a fishing boat from Dubai and Kuwait and sent them to the Persian Gulf to identify our defence systems," he said. "But when we arrested them, they said they had come for fishing and were tourists."

Human Rights Watch called Emami's death "suspicious" on Tuesday (13 February) as the group urged Iranian authorities to investigate.

Sarah Leah Witson, HRW's Middle East director, said: "Iranian judicial authorities think they can get away with claiming that Seyed Emami, a well-known professor, simply committed suicide while being detained in one of the highest-security wards of Evin prison.

"The Iranian judiciary long ago lost its credibility after failing to investigate repeated incidents of torture and mistreatment in detention."

Emami's is the third alleged suicide in detention to be reported by Iranian authorities since the start of the year.