CAIRO - A bomb near an army intelligence building wounded four soldiers Sunday, the third such blast within a week in Egypt after the Muslim Brotherhood's terrorist designation further polarised the country.
The explosion, which the army said was a "cowardly terrorist" act, comes as the military-installed authorities plan to hold a referendum on a new constitution next month - the first step toward democracy since the ouster of Islamist president Mohamed Morsi in July.
Sunday's explosion occurred in the Sharqiya province in the Nile Delta and destroyed the rear compound wall of the intelligence building, the army said, adding four soldiers were wounded.
The blast was the third such attack in less than a week.
But another was averted on Sunday when a bomb was found and defused by experts near the gate in front of Al-Azhar's medical faculty in New Damietta city, north of Cairo, security officials said.
On Tuesday, a suicide car bomber killed 15 people at a police building in Mansoura, north of Cairo. And on Thursday a bomb in Cairo wounded five people on a bus.
The Mansoura attack, one of the deadliest attacks since Morsi's ouster, triggered outrage among the authorities and Egyptians at large.
A day after that attack, which was claimed by Al-Qaeda-inspired jihadists, the authorities accused the Brotherhood of perpetrating it and listed the Islamist movement to which Morsi belongs as a "terrorist organisation".
But the Brotherhood, which prevailed in all elections since the ouster of strongman Hosni Mubarak in early 2011, said it is "innocent of any violent incident that has (been) or will be committed".
The terrorist designation represents the hardening of an ongoing government crackdown against Morsi's Islamist supporters.
It means hundreds of thousands of Brotherhood members now face prison sentences if they hold demonstrations or are found in possession of the movement's recordings or literature.
The designation carries possible death sentences to Brotherhood leaders.
Arrests in Alexandria
On Sunday, in the Mediterranean city of Alexandria the police arrested three people, including two minors, after they searched a printing press in which they found propoganda materials supporting the Brotherhood and opposing the security forces.
The crackdown on Morsi's supporters launched since his ouster by the military on July 3 has seen more than 1,000 people killed and thousands of the toppled president's backers arrested.
But despite the repression, the Brotherhood has been holding demonstrations across Egypt, especially in the past three days, with at least seven people killed in clashes between Morsi's supporters and opponents.
Egypt's universities witnessed severe clashes this week, and on Saturday a 19-year-old student was shot dead in clashes at Al-Azhar's Cairo campus, where pro-Morsi students have regularly staged protests.
The students entered the commerce faculty of the university during an exam and set it alight, before police burst into the campus and fired tear gas.
A police official said 101 students were also arrested after the fire on the first two floors of the building was brought under control.
The violence came a day after five people were killed in clashes across Egypt, as police stamped out Brotherhood demonstrations.
The interim authorities have decapitated the 85-year-old Brotherhood, imprisoning Morsi and most of the movement's leadership and putting them on trial.
They face trial for allegedly colluding with militants to launch attacks.
More than 100 soldiers and policemen have been killed in the Sinai since Morsi's ouster.
Egypt's first democratically elected president, Morsi ruled for just one turbulent year before the military overthrew him following mass protests demanding his resignation.