Cairo (AFP) - A bomb claimed by an Islamist group exploded outside the gates of Cairo University Wednesday, an Egyptian police official said, wounding at least nine people, including a senior officer.

Scores of policemen and soldiers have been killed in militant attacks, mainly in the Sinai Peninsula, since the military overthrew Islamist president Mohamed Morsi last year and crushed his supporters.

Ajnad Misr, a militant group that has killed several policemen in Cairo bombings, claimed Wednesday's attack, saying on Twitter it was in response to repression of students.

It had pledged retaliation last week after police quashed protests in universities across the country.

A student at Alexandria University died of gunshot wounds sustained during the clashes.

The assistant police chief of Cairo's Giza district was moderately wounded in Wednesday's blast alongside five other policemen stationed outside the campus to quell protests and three civilian passersby, an interior ministry official said.

Police cordoned off the area and scoured it with sniffer dogs.

The explosion occurred near the site of a bombing in April that killed a police general, and where riot policemen are stationed on foot and in armoured vehicles to confront frequent protests by pro-Islamist students.

Police had clashed with students earlier in the day, an official said.

April's attack was claimed by Ajnad Misr as retaliation for the deadly crackdown on Morsi's supporters that left hundreds dead in street clashes and thousands in jail.

The group also claimed responsibility for bombing a checkpoint outside the foreign ministry last month that killed two policeman.

And a bombing on October 15 wounded 12 civilians near a main court complex. Ajnad Misr condemned that attack, saying it only targets security personnel.

The authorities have blamed Morsi's now blacklisted Muslim Brotherhood for the violence, although the group insists it is committed to peaceful protests.

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President Abdel Fattah al-Sisi, the army chief who overthrew Morsi and was subsequently elected, has vowed to eradicate the Islamist movement, which continues to hold small protests.

Police said Wednesday they arrested 12 pro-Brotherhood students in campus clashes.

It is thought that more Brotherhood-linked activists are embracing militant tactics as police squeeze the protests, which are often swiftly dispersed.

At least 15,000 Islamists have been arrested on suspicion of protesting or participating in violence since Morsi's overthrow.

More than 200 have been sentenced to death for taking part in deadly riots in August 2013, after police killed hundreds of pro-Morsi protesters in clashes in Cairo.

Morsi himself is standing several trials on charges ranging from espionage to militancy, and could be sentenced to death if convicted.