Iran's English-language Press TV said the ministry had "called on Tehran's governor's office to identify those involved" in Sunday night's incident. It did not make clear whether the ministry itself would also look into it.

It came a day after Iran's influential speaker of parliament, Ali Larijani, condemned the attack on the dormitory of Tehran University.

One student activist who declined to be named told Reuters on Tuesday that four students -- three men and one woman -- were killed during the violence.

Tehran University Chancellor Farhad Rahbar denied anyone had been killed, the students news agency ISNA reported.

The incident took place during widespread street unrest sparked by official results showing hardline President Mahmoud Ahmadinejad won a landslide against moderate Mirhossein Mousavi in last week's election.

Thousands of students have joined protests against what they say was a rigged vote, a charge dismissed by the authorities. Anti-Ahmadinejad demonstrators and riot police have clashed in the capital Tehran and elsewhere.

Hundreds of students staged a sit-in protest for a second day on Wednesday against the dormitory attack and suspected election irregularities, an activist told Reuters.

Press TV said the Tehran governor's office had also been told to "deal with complaints" made by the students.

Iran's most prominent university has traditionally been a hotbed of dissent, before and after the 1979 Islamic revolution.

Larijani, a conservative who has been critical of Ahmadinejad in the past, said on Tuesday the Interior Ministry should be held accountable for the university incident as it was in charge of security.

He did not say who had carried out the attack, but students told Reuters members of the religious Basij militia and plain-clothes policemen did it.

Basij is a volunteer paramilitary force fiercely loyal to Supreme Leader Ayatollah Ali Khamenei who has the final say on all matters of state in Iran.

During the past three days of violence, police have accused "bandits" of setting buses on fire, breaking windows of banks and other buildings, and damaging public property.