At least 14 people have been killed and dozens injured in a car bomb blast at the police headquarters to the north of the Egyptian capital Cairo, local reports say.
The blast in Egypt's Nile delta city of Mansoura, the capital of Dakahliya Governorate, at about 01:00 local time (23:00 GMT), is said to have brought down a section of the building.
Egypt's health ministry said the casualty figures are likely to increase as several people are feared trapped under the partially collapsed building.
The blast was so powerful that it damaged several nearby buildings and vehicles.
Unconfirmed reports suggest that there were two blasts and a third explosive was defused by the authorities. No group has claimed responsibility for the attack.
"This is an act of terrorism that aims at frightening the people and obstructing the road map" Egypt's interim prime minister Hazem el-Beblawi told the ONTV channel.
"The black hands behind this act want to destroy the future of our country. The state will do its utmost to pursue the criminals who executed, planned and supported that attack."
The interim administration has blamed the outlawed Muslim Brotherhood, the outfit led by ousted president Mohamed Morsi, for the bombing.
"Prime Minister (Hazem) Beblawi has declared the Muslim Brotherhood as a terrorist organisation," said spokesperson Sherif Showky, according to the Middle East News Agency (Mena).
However, the Muslim Brotherhood wrote on its Twitter account that the Islamist group "strongly condemn the cowardly bombing in Mansoura & express deep condolences to families of the victims of Egypt".
The Brotherhood has been calling for the reinstatement of Morsi as president ever since he was ousted in July during a military coup.