A statement issued by the group, which has been declared a terrorist organization by the United States and European Union, said it had decided "not to stand idly by in the face of senseless scenes on the street," Asharq al-Awsat reported Tuesday.
The move comes as police went on strike, demanding better conditions and weapons, the newspaper said. Rioting was reported in Cairo, Port Said, Alexandria, Assiut, Mahala and Mansoura.
Assem Abdel-Magid, who is organizing the militias, issued a general call to the public in Cairo, asking people to join forces and confront the violence, the newspaper said
A statement recently issued by the prosecutor-general was interpreted as opening the way for vigilantism, the newspaper said. The statement said the prosecutor-general "urges all citizens to exercise the right ... to arrest anyone found committing a crime and refer them to official [security] personnel."
Hours later, a second statement was released saying the initial statement "did not include granting 'judicial arrest' powers to citizens, but rather granting these judicial arrest powers to officers," the newspaper said.
The Muslim Brotherhood's Freedom and Justice party issued a statement saying the role of the police cannot be carried out by any other institution or group.
Interior Minister Mohamed Ibrahim said he would not allow vigilante groups or militias to take over security duties, the newspaper said.