Katherine Butler: Ahmadinejad's creaking regime feels heat after death of martyr

A computer science student has become the newest and highest-profile "martyr" for the cause of reformists in Iran and the latest threat to the rattled Islamic regime as it tries to keep a lid on a pressure cooker of simmering discontent.

Mohsen Ruholamin, 25, was picked up on 9 July at a demonstration marking the anniversary of a 1999 student crackdown. Twelve days, later his family was told he had died.

Campaigners have documented several shocking cases of young protesters dying in detention at the notorious Evin prison north of Tehran since the disputed presidential elections in June, their battered bodies handed back to their families for hasty burial so as to prevent anti-regime protests.

But Mr Ruholamin's case is different: he was the son of Abdulhosein Ruholamin, a high-ranking regime official who served as an aide to the conservative politician Mohsen Rezai, a candidate in the elections on 12 June. An account of how a shocked Dr Ruholamin, formerly the head of the Pasteur Institute, a prestigious science research body, first saw his son's disfigured corpse is now circulating in Iran. The circumstances of his death are deeply embarrassing for the shaken regime and risk igniting further unrest. "When I saw my son's face, it was clear that his mouth was smashed," his father said. "With the help of someone in authority I was allowed, as a privilege, to see the medical report. Location of death was erased but I found out he was wounded and not taken care of, then his blood became infected and he had a fever of over 40C, and then he got meningitis. I know my son was an honest boy and he could not lie – they could not stand his honesty."

Opposition leaders are seeking permission to hold a peaceful commemoration for all the "martyrs" on Thursday. Mirhossein Mousavi, the defeated presidential candidate, warned yesterday of further trouble if arrests continued. It is unlikely, however, that authorities preoccupied by a tense internal power struggle among hardliners will sanction anything that could turn into a show of strength by the opposition.

The increasingly embattled President, Mahmoud Ahmadinejad, sacked his Intelligence Minister on Sunday, a day after being forced by his chief backer, Iran's spiritual leader Ayatollah Ali Khamenei, to withdraw the appointment of his son-in-law as vice-president.