CAIRO - Two bombs targeting security posts near Cairo University exploded in quick succession on Wednesday killing a police general, followed by a third blast as police and journalists gathered at the scene.
An assistant interior minister was wounded in the double bombings, police said.
Witnesses said the explosions sent up a cloud of smoke and dust near the campus in the centre of the Egyptian capital, the scene in the past few months of repeated clashes between Islamist students and police.
The third bomb went off near the campus main gates, where police investigators and journalists had gathered following the first blasts.
An AFP correspondent at the site said the explosion threw several policemen to the ground.
The attack was the latest by militants targeting security forces following Islamist president Mohamed Morsi's overthrow in July.
It 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 elections 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.
A 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 student in Cairo University said he ran out of the campus after hearing the explosions.
"I found a lifeless man in plain clothes and a policeman bleeding from his leg," said the student, Amr Adel.
Mergawi was a chief detective who would have been dressed in civilian clothes.
Cloud of smoke, dust
Amateur footage of the bombings posted on an Egyptian newspaper's website showed policemen running out from a cloud of smoke and dust sent up by the first explosion.
The second bomb went off moments later.
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.
Most of the attacks have taken place in the Sinai Peninsula, a hub of militant activity, but the jihadists have increasingly targeted police in the capital and the Nile Delta.
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.
The Brotherhood, now decapitated with Morsi and much of its leadership in jail, has been designated a terrorist group in Egypt and its close ally Saudi Arabia.
Some of its top leaders have relocated to London, where British Prime Minister David Cameron has ordered a probe into the group's activities.
Militants are expected to increase their attempts after Sisi announced his candidacy for the election in late May, which he is likely to win.
But police have scored some successes in their fight against the jihadists, killing and capturing members of two major cells in the Nile Delta over the past two months.
One of the cells, belonging to Ansar Beit al-Maqdis, was implicated in the car bombing of Cairo police headquarters in January.
The Muslim Brotherhood, meanwhile, has insisted it remains committed to peaceful action and said it would continue its protests, which often descend into violent clashes with police.
More than 1,400 people, mostly Islamists, have been killed in such street clashes since Morsi's overthrow.