The military-backed interim Egyptian government has declared the Muslim Brotherhood a terrorist group.
由军方支持的埃及临时政府宣布穆斯林兄弟会为恐怖组织。
Supporters of Mohammed Morsi have held demonstrations since 3 July
The group, whose candidate Mohammed Morsi won the presidential poll last year before being deposed by the military, had already been outlawed.
Thousands of its supporters have been arrested in a crackdown.
A Muslim Brotherhood leader in exile vowed that protests would continue.
'Horrified'
Deputy Prime Minister Hossam Eissa announced the move, which will give the authorities more power to crack down on the Brotherhood.
He said that those who belonged to the group, financed it or promoted its activities would face punishment.
The decision was in response to Tuesday's suicide bombing of a police headquarters in Mansoura, in the Nile Delta, which killed 16 people and wounded more than 100, he said.
"Egypt was horrified from north to south by the hideous（丑恶的） crime committed by the Muslim Brotherhood group," Mr Eissa said.
"This was in context of dangerous escalation to violence against Egypt and Egyptians and a clear declaration by the Muslim Brotherhood group that it still knows nothing but violence.
"It's not possible for Egypt the state nor Egypt the people to submit to the Muslim Brotherhood terrorism."
Egypt would notify Arab countries who had signed a 1998 anti-terrorism treaty of the decision, he added.
The Brotherhood has denied being responsible for the attack, and an al-Qaeda inspired group has claimed responsibility.
Ibrahim Munir, a member of the group's guidance council who is in exile in London, told AFP news agency that the government's decision was "illegitimate".
He added: "The protests will continue, certainly."