The Egyptian government has declared the Muslim Brotherhood a terrorist group.
The move was officially announced by Hossam Eissa, the minister of higher education, who read out the Cabinet statement on state television on December 25.
It criminalizes all the brotherhood's activities as well as its financing, and membership of the group.
Recently ousted President Muhammad Morsi belongs to the brotherhood movement.
The group's supporters have been waging protests since the overthrow of Morsi on July 3.
Egyptian authorities blame the brotherhood for a series of militant attacks, including a suicide attack on police headquarters in Sinai that killed 16 people and wounded more than 100.
The Brotherhood has repeatedly denied the claim and has condemned the bombing.
Prime Minister Hazem al-Beblawi described the Brotherhood as a terrorist group, but the announcement on December 25 formalizes this designation.
Meanwhile, an Al-Qaeda-inspired militant group has said it carried out the attack.
In a statement posted on a militant website, Ansar Beit al-Maqdis said the attack on December 24 was carried out by a suicide bomber identified as Abu Mariam.
Ansar Beit al-Maqdis had previously claimed responsibility for a series of attacks, including a failed assassination bid against Interior Minister Mohammed Ibrahim in Cairo in September.
In related news, Egyptian police have arrested Hisham Qandil, who served as the country's prime minister under Morsi.
Authorities said Qandil was arrested for failing to obey a court order while he was in office.
In April, a court sentenced him to one year in prison for failing to carry out an order to renationalize a company that had been sold off in 1996.
Based on reporting by AP, AFP, Reuters, dpa, and the BBC