Blast at Egypt security site kills 14

A powerful car bomb explosion has rocked a police headquarters in an Egyptian city north of Cairo, killing at least 14 people and injuring 120, officials said.

An interim government spokesman accused the Muslim Brotherhood of orchestrating the attack and branded it a "terrorist organisation." The Brotherhood then quickly condemned the blast in an emailed statement. 

The Prime Minister Hazem el-Beblawi described the attack as a "terrorist incident," and vowed that the perpetrators "will not escape justice.''

"The Muslim Brotherhood considers this act as a direct attack on the unity of the Egyptian people and demands an enquiry forthwith so that the perpetrators of this crime may be  brought to justice," the statement said.

The Middle East News Agency quoted Cabinet spokesman Sherif Shawki as saying that the Muslim Brotherhood showed its "ugly face as a terrorist organisation shedding blood and messing with Egypt's security."

Sections of the five storey building in the Nile Delta  city of Mansoura collapsed after the blast early on Tuesday and police evacuated surrounding buildings.

The bombing comes weeks before Egypt is to hold a referendum on a new constitution, billed by the army-backed government as the first step towards democracy since the military toppled former president Mohamed Morsi in July.

No group claimed responsibility for the attack, but Fahmy said early information indicated that the attackers may have had inside information about who was at a meeting in the building.

Omar al-Shawatsi, the governor of Dakhalya, of which Mansoura is the capital, told state media all of the casualties were police.

"The explosion was caused by a car bomb," Shawatsi said.

The impact of the explosion was felt around 20 kilometres away and shattered the windows of nearby buildings, security sources said.

The Daqahleya region's head of security, Sami El-Mihi, was wounded in the blast and two of his aides were killed, security sources said.