Thirty-six Islamist prisoners have been killed in Egypt during an attempted prison break, state media is reporting.
"A security official has confirmed that 36 Muslim Brotherhood elements were killed during an attempt to escape," the official MENA news agency reported.
The agency reported that "unknown gunmen" had tried to aid the prisoners, who kidnapped a police officer.
Earlier, the interior ministry said the inmates rioted while they were being transferred to the north Cairo prison of Abu Zaabal, and that police were "dealing with the situation".
The deaths come as an Islamist alliance opposed to the Egyptian military's ouster of president Mohamed Morsi has called off rallies that they planned to stage in Cairo, citing concerns about security.
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"Several marches in Cairo have been cancelled for security reasons," said Yasmine Adel, a spokeswoman with the Anti-Coup Coalition.
She said some other marches were taking place, however, but it was not immediately possible to confirm.
In central Cairo's Dokki neighbourhood, residents took over a mosque the Islamists had planned to use as a starting point for a march and put up a poster of a slain policeman, an AFP correspondent said.
Vigilantes stopped cars with bearded people and took them out, the correspondent said.
