The BBC's Jon Leyne: "The future direction of Iran is at stake"

A statement read out on Iranian TV said General Muhammad Ahmadi and his unnamed deputy have been handed over to judiciary officials.

On Sunday thousands of students took to the streets of Tehran and other major cities for a fourth consecutive day of protests in the most serious challenge to the Islamic regime since the 1979 revolution.

The students in Tehran have now dispersed for the night, heeding pleas from President Muhammad Khatami and his pro-reform government.

Mr Khatami had warned that further disturbances would damage his programme of careful democratic change, which the students support.

The demonstrators had been demanding the arrest and execution of Iran's hardline top policeman, General Hedeyat Lotfian, and for control of law-enforcement agencies to be transferred from the Islamic authorities to President Khatami.

The National Security Council, headed by the president himself, had earlier promised to punish the leader of a police operation in which five students were reportedly killed.

Several hundred students at a Tehran hostel had been staging a peaceful demonstration in support of press freedom when they were attacked on Friday by police and anti-reform vigilantes.

BBC Middle East Correspondent Jim Muir says conservatives got a glimpse of popular support for reforms

The incident caused outrage among pro-reform politicians. President Khatami expressed his "deep regret" for the police raid, calling it an "ugly and bitter incident".

Demonstrators earlier shouted slogans calling on Iran's supreme leader, Ayatollah Ali Khamenei, to intervene to prevent further attacks. Accusations of his alleged complicity in the student deaths were also chanted.

Police kept away and the protesters placed blockades of tires and barbed wire across roads near the university.

Multiple resignations

On Sunday the chancellor of Tehran University and the heads of 18 faculty departments resigned in protest at the police action.

The faculty heads described the incident at the hostel as an "unprecedented crime in our university's history".

The Minister of Higher Education, Mostafa Moin, also offered his resignation but Mr Khatami is reported to have rejected it.

Press protest

More than 500 journalists working for pro-reform newspapers have added their voice to the protests by announcing a one-day strike against the closure of Salam to take place on Tuesday.

Criticism of supreme leader Khamenei has been taboo before this

The new press curbs are seen as part of a protracted struggle between President Khatami and hardline religious conservatives.

Ayatollah Khamenei, who is supreme leader of the Islamic revolutionary state, is identified with the reactionaries but has always avoided comment on the reform debate.