Two bombs targeting security posts near Cairo University have exploded in quick succession, killing a police general, followed by a third blast as police and journalists gathered at the scene.
A fourth bomb placed in a car parked near the university was defused, security officials and state television said.
An assistant interior minister was wounded in the double bombings in the centre of the Egyptian capital on Wednesday, police said.
Witnesses said the blasts sent up a cloud of smoke and dust near the campus, the scene in past few months of repeated clashes between Islamist students and police.
The third bomb struck close to the campus main gates, where police investigators and journalists had gathered, but the official MENA news agency reported it caused no injuries.
The attack was the latest by militants targeting security forces since Islamist president Mohamed Morsi's overthrow in July and came less than a week after the military chief who overthrew Morsi, Abdel Fattah al-Sisi, said he was quitting the army to run in presidential election in May, vowing to wipe out "terrorism".
The first two rudimentary bombs also wounded five policemen, the interior ministry said, identifying the slain officer as Brigadier General Tarek al-Mergawi.
Another police general at the scene told AFP that the bombs were concealed in a tree between two small police posts.
"I was waiting for the bus when I heard two explosions. There was dust in the air and policemen were screaming," said a witness, Sakta Mostafa.
A Cairo University student said he ran out of the campus after hearing the blasts.
"I found a lifeless man in plain clothes and a policeman bleeding from his leg," said the student, Amr Adel.
As a chief detective, Mergawi would have been in civilian clothes.
Major General Abdel Raouf al-Serafi, an assistant interior minister, was among the wounded, police officials said.
The government says militants have killed almost 500 people, most of them policemen and soldiers, in attacks since Morsi's overthrow amid a deadly crackdown on his Islamist supporters.
The government generally blames Morsi's Muslim Brotherhood for the violence, although the deadliest bombings and shootings have been carried out by the Al-Qaeda inspired Ansar Beit Al-Maqdis group, based in Sinai.
