Egypt's military-backed interim government is stepping up its crackdown on the Muslim Brotherhood, a day after declaring the group a terrorist organization.
State media say authorities have arrested 16 Brotherhood activists in the Nile delta province of Sharkiya on suspicion of promoting the group's ideology, distributing leaflets, and inciting violence against the army and police.
In Cairo, a bomb blast near a public bus at a busy intersection wounded five people. Security officials say they defused a second bomb attached to a nearby billboard.
The bus driver, Adel Abdel Fattah, described what he experienced.
"While I was driving the bus, an explosion hit the bus and all of the bus windows were smashed and four people were injured, including one in serious condition."
The Interior Ministry described the attack as an attempt to intimidate voters ahead of a referendum next month on a new constitution. The vote is billed as part of a democratic transition ahead of elections for a new parliament and president.
The constitution will replace one adopted while the Muslim Brotherhood controlled Egypt's parliament and the movement's Mohamed Morsi was Egypt's first democratically elected president.
The interim government declared the Muslim Brotherhood a terrorist organization Wednesday after blaming it for a car bomb attack that killed 15 people at a police headquarters of Mansoura, north of Cairo, the day before.
The declaration broadened the government's authority to move against the group -- strengthening a crackdown that has been under way since the army ousted Mr. Morsi in July.