A little-known jihadist group, Ajnad Misr, claimed a series of attacks and vowed new ones targeting Egyptian security forces in a video posted on its Twitter account on Thursday.
In the video titled "Retaliation is life", the group said that it had carried out eight attacks in Cairo since November 20, 2013.
It also said it would launch new attacks as revenge against the abuses inflicted by security forces on women protesters supporting ousted Islamist president Mohamed Morsi.
"Our honour is screaming and asking whether there is a man to retaliate or has manhood died?", the video said.
It promised to "mothers of those (protesters) killed and detained ... that very soon they would be pleased," suggesting it would carry out more attacks.
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The video showed policemen dragging women protesters, and also displayed a pool of blood from a police crackdown on a sit-in of Morsi supporters at Cairo's Rabaa al-Adawiya Square on August 14.
Hundreds of people were killed that day when police stormed the square after pro-Morsi supporters refused to leave it.
They were demanding reinstatement of Morsi, who was ousted by the army on July 3.
Since Morsi's ouster, Egypt has been rocked by deadly bombings and shootings targeting security forces.
The deadliest attacks have been claimed by Sinai-based Ansar Beit al-Maqdis, a jihadist group inspired by Al-Qaeda. It has carried out attacks in the restive Sinai Peninsula as well as in the Nile Delta and in Cairo.
But Ajnad Misr (Soldiers of Egypt) claims it has carried out attacks only in Cairo, including the killing of a police general near Cairo University earlier this month.