AT least 14 people were killed when a powerful explosion rocked an Egyptian police headquarters in a city north of Cairo early today.
The blast was believed to be caused by a car bomb, and Egypt's interim government accused the Muslim Brotherhood of orchestrating the attack, branding it a "terrorist organisation".
The Middle East News Agency (MENA) 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".
No one immediately claimed responsibility for the bombing in Mansoura, 70 miles north of Cairo, which also injured dozens.
The attack came a day after an al Qaida-inspired group called on police and army personnel to desert or face death at the hands of its fighters.
The militant group, based in Egypt's volatile Sinai, and several others have claimed responsibility for a surge of attacks on security forces since a coup in July toppled the country's Islamist president, Mohammed Morsi, who hails from the Brotherhood.
In response, Egypt's armed forces launched an offensive against militants in the northern part of the Sinai Peninsula in August.
According to MENA, the explosion took place at 1.10am local time at the security headquarters in Mansoura, in the Nile Delta province of Daqahliya, collapsing part of the five-floor building.
A security official says 14 people were killed and nearly 100 injured, including the city's security chief. Most of those who died were police officers inside the headquarters, their bodies buried beneath the debris.
It was the first major attack in the Nile Delta, spreading the carnage to a new area and bringing it closer to Cairo. Previous violence that killed scores of people happened in Sinai, or in Suez Canal-area cities such as Islamilia.
Shortly after the Mansoura bombing, security forces cordoned off the whole area, closed major entrances and exits to the city and set up checkpoints to search for perpetrators, the official said.
The death toll is expected to rise, he said. State TV called on residents to rush to hospitals to donate blood.
He added that the preliminary investigation indicated a car bomb caused the explosion. The explosion also damaged surrounding buildings, including a bank and a theatre, and wrecked dozens of vehicles, MENA said.
Egypt's Prime Minister Hazem el-Beblawi described the attack as a "terrorist incident," expressed condolences to the families of the victims and vowed that the perpetrators "will not escape justice".
Today's bombing was not the first time that the security headquarters in Mansoura was targeted. Weeks ago, an explosion went off in front of the building but caused no casualties.
Since the summer coup that ousted Mr Morsi, militant Islamists have attacked several security headquarters with car bombs or by suicide bombers.
The Mansoura attack came shortly after the Islamic militant group Ansar Beit al-Maqdis, or the Champions of Jerusalem, threatened more attacks on the military and police, saying it considers Egyptian troops to be infidels because they answer to the secular-leaning military-backed government.
The group and others based in the Sinai have claimed responsibility for a number of suicide car bombings and deadly attacks on security headquarters, including a failed assassination attempt on Egypt's Interior Minister in September with a suicide car bombing. The minister escaped unharmed.
Egypt's military spokesman Ahmed Mohammed Ali said yesterday the army crackdown has killed 184 militants and arrested 803 others. He said about 25% of those killed and arrested are foreign fighters.
Ansar Beit al-Maqdis is believed to have ties with Palestinian militants in the neighbouring Gaza Strip, and officials have said other foreign militants have found refuge in Sinai during the turmoil.
In yesterday's message, it said it "will be more determined to fight" the military and police if its warning is ignored.
It urged them to "repent" from participating in "this infidel bastion that is at war with God and his Prophet, and stop serving in its ranks".