A bomb exploded at a police station in a province north of Cairo early on Wednesday (local time), killing one person and wounding 17 others, Egyptian Health Ministry and security sources have said.
Unknown assailants threw the bomb from a passing car in Mansoura, the capital of Dakhalia province, two security sources said.
A Health Ministry statement, issued shortly after the explosion, said 12 people were injured. The bombing occurred after a day of clashes between opponents and Islamist supporters of Egypt's deposed president, Mohamed Mursi, killed nine people in Cairo.
The Muslim Brotherhood, which propelled Mursi to power in the country's first democratic elections in 2012, accuses the army of orchestrating a coup that has exposed deep political divisions in the Arab world's most populous nation.
Supporters of Mursi, who has been held in an unknown location since the army deposed him on July 3 following mass protests calling for his removal from power, have vowed to stay in the streets until he is reinstated.
About 100 people have died in violence since the army deposed Mursi and replaced him with an interim administration led by Adli Mansour, the head of the constitutional court. New elections are expected to be held in about six months.
In the latest bout of violence in the capital, two protesters were killed at a pro-Mursi march early on Wednesday after clashes in Cairo, a security source and the Muslim Brotherhood said in a statement on their website.