CAIRO — A homemade bomb exploded alongside a public bus near a Cairo university campus, wounding at least five people and underscoring concerns that a spate of attacks blamed on Islamists was moving to the capital.

The blast near the Al-Azhar University campus came two days after a deadly attack on a Nile Delta police headquarters that prompted the military-backed government to brand the Muslim Brotherhood a terrorist group. The designation yesterday opened the door for even harsher measures against the Islamist group that fielded Mohammed Morsi for the presidency and became the target of a crackdown following his July 3 overthrow.

On Thursday, police arrested 16 Muslim Brotherhood supporters, the state news agency said, the first arrests on charges of belonging to a terrorist organization since the group was declared one by the government.

The bus bombing took place in the Nasr City neighborhood that has served as a Brotherhood rallying point for months. Five people were wounded, Ahmed El-Ansari, head of the nation’s ambulance service, said by phone; reports of one fatality could not be immediately verified. Authorities discovered at least two other devices at the scene, state-run Ahram Gate and state television reported.

Television footage showed a red public bus on the road, its back end partially charred by the blast near the campus, where security forces have clashed with students belonging to the Brotherhood in recent weeks.

The attack marked a shift away from earlier violence that has largely targeted security officials, including an attempted assassination on Interior Minister Mohamed Ibrahim in September.

It also intensified broader worries that the Dec. 24 suicide attack outside the security headquarters in the Nile Delta city of Mansoura marked an attempt to expand the reach of insurgent violence that has largely been contained to the restive Sinai and the Suez Canal areas.

The Mansoura explosion, which left 16 dead and over 100 wounded, was the deadliest single assault on security forces outside the Sinai since Morsi’s ouster. The government, without providing evidence, first hinted the Brotherhood was to blame, then blacklisted it as a terrorist organization yesterday.

The unprecedented move means that anyone who takes part in the group’s activities or promotes it, even verbally, can be punished by law, according to a Cabinet statement. The Interior Ministry said in an e-mailed statement today that it had implemented a Cabinet order barring the publication and distribution of the newspaper belonging to the Muslim Brotherhood’s political arm, the Freedom and Justice Party.

Authorities have already arrested and prosecuted many of the organization’s leaders, including the ousted president, and killed hundreds of its supporters.

The Brotherhood decried the latest measure against it as the work of “terrorists” and “killers” who orchestrated the “coup” against Morsi. It vowed to press ahead with its near- daily protests demanding his reinstatement.

“The leaders of the bloody military coup think” that “their new terrorist plot will rescue them from retribution, gallows and popular anger,” the main pro-Morsi alliance, which includes the Brotherhood, said in a statement. The Anti-Coup Alliance pledged to continue “creative peaceful resistance, no matter what the sacrifices may be.”