Two Egyptian policemen and a civilian have been wounded in a bomb attack targeting a security checkpoint in central Cairo, officials and a medic said.
The device, which was placed by unknown assailants between two cars near the checkpoint at al-Galaa Square in Dokki neighbourhood, exploded at about 7:15 am local time on Tuesday, AFP news agency quoted a security official as saying.
Police sealed off the area and bomb disposal experts were examining the site to make sure no other bombs were planted nearby.
Egypt has been rocked by a series of bombings and shootings carried out by armed men since the military toppled the first freely-elected president, Mohamed Morsi of the Muslim Brotherhood, in July.
Most attacks have been in the restive Sinai Peninsula, but in recent months brazen attacks have also been launched farther afield in the Nile Delta and in the capital Cairo.
Student protester killed
The explosion comes a day after a student was killed on Monday in clashes between police and anti-coup protesters at Cairo University, Reuters news agency quoted a medic as saying.
Security forces fired tear-gas at protesters who in turn hurled fireworks and at least two petrol bombs at police lines, Reuters reported. A reporter for a local newspaper was also wounded when he was hit by birdshot, the paper said.
With the state cracking down hard on opposition groups, the universities have become a major arena for protests by those opposing last July's military topple of Morsi.
The Anti-Coup National Alliance had called for a week of "non-violent defiance and a huge revolutionary Monday in solidarity with detainees and martyrs' families".
The protests often lead to confrontation between the security forces and demonstrators.