The bus was carrying 30 students along a mountainous road within the university's science and research campus in northwestern Tehran when it veered off the road and hit a concrete colu

They demanded the university's chairman of the board of trustees Ali-Akbar Velayati resign, the sports and youth ministry's news agency Borna reported.

The demonstrating students reportedly carried photos of victims of Tuesday's crash at a square leading to the university, in a rare display of dissent at Tehran's Islamic Azad University.

Hundreds of Iranian students held protests for a second day on Sunday, calling for university officials to resign over a bus crash that killed 10, state news agency IRNA said.

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Seven were killed instantly, state TV said, while an updated death toll of 10 was reported by the conservative Tasnim news agency the day after the crash.

The university initially blamed Tuesday's crash on the driver having a stroke, which was later denied by the coroner's office.

On social media, the public and students have pointed to the university's ageing bus fleet and poor maintenance.

Several mid-tier managers were fired in the wake of the accident and some arrested, the university told semi-official news agency ISNA on Wednesday.

Students have called for the university's bus fleet to be replaced.

They want an emergency centre to be set up on-campus and for guard rails to be erected along the entire mountainous road where the accident happened.

Iran's prosecutor general Mohammad-Jafar Montazeri visited the protesting students and called for calm.

He promised them he would follow up on the case personally and punish wrongdoers "if they were found guilty."

Iran is the world's seventh deadliest country per capita for road accidents, according to 2013 data -- the latest available -- published by the World Health Organisation.

Efforts to modernise Iran's ageing and highly polluting vehicle fleet have been hampered by a lack of investment.

Foreign companies Peugeot and Renault were forced to withdraw this year due to the return of US sanctions.