People run away after the third blast outside Cairo University, Giza, Egypt, Wednesday, April 2, 2014 (Photo: Mai Shaheen)
Three bombs have exploded at Cairo University, killing one policeman and injuring at least five others.
A fourth device was deactivated.
Shortly before midday, two explosions took place near a police guard post outside the university, according to Hesham Youssef, the head of the explosives section at Giza security directorate.
At around one o'clock, a third bomb went off in a tree near the university's front gate.
They were detonated remotely.
Police are searching the area for more devices, Youssef said.
Brigadier-General Tarek El-Mergawi was killed and at least five other policemen were injured in the first attack. There were no reported injuries in the second attack.
El-Mergawi was the head of West Giza investigative police.
Fifteen students have been arrested in the vicinity of the university and taken to Giza security directorate for questioning, a police source told Ahram Online.
The first explosions caused part of a building to collapse, eyewitnesses said.
The university has been evacuated and the area cordoned off by police.
Prosecutor-General Hesham Barakat has ordered an investigation into the attack and called for the perpetrators to be indentified and brought to justice.
A team of investigators arrived at the scene and are questioning the injured and eyewitnesses.
Universities have become a key venue for protests in support of deposed president Mohamed Morsi.
Clashes have frequently broken out between pro-Morsi students and security forces since the beginning of the new semester, which was delayed for three weeks due to security concerns.
Two students died in clashes between protesters and police earlier this week at Al-Azhar University in Cairo.
On 20 March, engineering students started a strike in protest against on-campus violence the day before, in which security forces clashed with pro-Brotherhood students.
Also on 20 March, explosives experts defused two bombs at the law faculty of Cairo University.
In February, the interim authorities issued a decree allowing security forces to enter campuses and granting university administrators the right to expel protesting students.
Militant attacks have killed 496 people in Egypt since the ouster of president Mohamed Morsi in July, according to a foreign ministry statement.
The statement said 252 police and 187 military personnel were among those killed, in addition to 57 civilians.
The military has killed dozens of suspected militants and razed dozens of buildings since its counter-insurgency offensive in the Sinai Peninsula began in summer 2013.
On 5 September, there was a failed assassination attempt on Interior Minister Mohamed Ibrahim.
On 24 December, a large explosion hit the Daqahliya security directorate in Mansoura, killing 15 and injuring over 130 policemen and civilians.
Sinai-based militant group Ansar Beit Al-Maqdis has claimed responsibility for most of the attacks.