An explosion outside Cairo University wounded at least seven people on Wednesday, among them police and civilians, security sources said.
There was no immediate claim of responsibility.
Islamist militants have carried out a series of attacks against police and soldiers, mainly in the remote but strategic Sinai region, since the army ousted President Mohamed Morsi of the Muslim Brotherhood last year after mass protests against his rule.
Cairo University was a focal point for protests against the government that succeeded Morsi until authorities tightened security with the start of the new term this month.
Egypt has cracked down on the Brotherhood and declared it a terrorist organization, but the group says it is peaceful.
Attacks in the capital are less common than in Sinai but when they do occur, they tend to prompt questions about the effectiveness of the government's efforts to end the bloodshed that has hit tourism, a pillar of the economy.
Join Jerusalem Post Premium Plus now for just $5 and upgrade your experience with an ads-free website and exclusive content. Click here>>