The Egyptian Interior Ministry has confirmed five people have been injured in a bomb blast on a bus in Cairo's Nasr City district on Boxing Day, just two days after a car bomb killed 16 in the Nile Delta.
The homemade device had been placed on a traffic island and exploded as a public bus passed by. A second one, found attached to an advertising billboard, was detonated by explosive experts, spokesman Hani Abdel Latif said. State television showed footage of a bus with its windows blown out.
Ministery spokesman Abdel-Fatah Osman told state TV said the bomb was planted near a school complex and intended "to terrorize people and cause chaos."
The site of the blast is also near student dormitories of the Islamic Al-Azhar University, which have been the scene of almost daily protests by Brotherhood students against Egypt's military-backed interim government.
Attacks across Egypt over the last few days have raised fears of intensifying violence in the run-up to a constitutional referendum in January as the interim government pushes ahead with an army-backed plan for political transition.
The attack also comes a day after the Muslim Brotherhood was declared a terrorist organisation by the interim government, criminalising all its activities, its financing and even membership to the group.
Hossam Eissa, the Minister of Higher Education said the decision was made in response to the bombing of police headquarters in the Nile Delta, north of Cairo on Tuesday. The Brotherhood has denied being responsible for Mansoura attack and an al-Qa'ida inspired group has claimed responsibility for the suicide bombing.
The most prominent militant group, Ansar Beit al-Maqdis, announced it carried out Tuesday's suicide bombing 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 coup.
The government has vowed to fight "black terrorism" after the deadly attack on a police compound in the city of Mansoura which also injured about 100 people.
Bomb attacks and shootings have become an almost daily occurrence in the Sinai peninsula since the army toppled Islamist President Mohamed Morsi on 3 July following mass protests against his rule.
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