CAIRO - An al-Qaida-inspired group based in Egypt's Sinai Peninsula claimed responsibility Wednesday for the suicide bombing of the police headquarters in a Nile Delta city that killed 16 people and wounded more than 100.
Ansar Beit al-Maqdis, or the Champions of Jerusalem, said it carried out the attack in Mansoura to avenge the "shedding of innocent Muslim blood" at the hands of Egypt's "apostate regime" - a reference to the security forces' crackdown on Islamists following the July 3 military coup that ousted Islamist President Mohammed Morsi.
While the claim posted on a militant website Wednesday could not be absolutely verified, it corresponded with previous messages issued by the group on the same forum. It identified the suicide bomber in Tuesday's attack by the nickname Abu Mariam.
"To the soldiers and officers we repeat our advice that you should leave service with the militias of (Defense Minister Gen. Abdel-Fattah) el-Sissi and (Interior Minister) Mohammed Ibrahim," the group said in a statement. "We call on you to stay clear from the security headquarters of this renegade regime to protect your own lives."
"Let everyone in this regime know that they are fighting against God and his prophet," the statement read. The group also urged Egyptians not to accept any constitution but "God's law."
The explosion in Mansoura, 110 kilometers (70 miles) north of Cairo, was the deadliest bombing yet in a months-long wave of violence blamed on Islamic militants.
The blast was so powerful it collapsed an entire section and side wall of the five-floor building, incinerating dozens of cars outside and damaging several nearby buildings. Egyptian state TV reported Wednesday that another of the wounded from the bombing had died, bringing the total death toll to 16.
Immediately after the blast, Egypt's military-backed interim government blamed the Muslim Brotherhood, the country's largest Islamist group - and the organization from which Morsi hails. The attack took place as top security officials reportedly were meeting in the Mansoura headquarters to work out arrangements for the Jan. 14-15 constitutional referendum.
The vote is a key step in the country's political transition after the military coup, but has sparked new Brotherhood protests. His group has staged continued protests since the July coup, demanding Morsi's release from jail and his reinstatement.
A security official said it appears the Mansoura bomber drove a pickup truck laden with explosives close to the police headquarters, then detonated it. The official, who spoke on condition of anonymity because he was not authorized to discuss the investigation with journalists, said that Cairo airport authorities arrested a Brotherhood member late Tuesday on suspicion that he was linked to the attack.
The suspect - identified as 22-year-old Adel Younis Rashid who runs a computer shop in Mansoura - was taken into custody as he was trying to fly to Turkey with his mother and a friend, the official said.
The suspect is the son of a leading Brotherhood member and former lawmaker from Mansoura, the official said, adding that authorities have confiscated Rashid's computers and telephones.
Ansar Beit al-Maqdis has emerged as the main Sinai-based militant group staging attacks against Egyptian security forces. The group has claimed most major attacks in the Sinai and Suez Canal-area cities in recent months, as well as a failed attempt to assassinate the country's interior minister in September.
On Monday, Ansar Beit al-Maqdis issued a message threatening more attacks against Egyptian troops, saying it considers them to be infidels because they answer to the secular-leaning government.
Associated Press writer Sarah El Deeb contributed to this report.