An Egyptian rights group has condemned the violations that women were subjected to during the latest sectarian confrontations in the Upper Egypt town of Beni Suef.

"Supporters of the Muslim Brotherhood stormed the Franciscan School in Beni Suef, detained three nuns from the school and then paraded them on the streets like prisoners of war," the Cairo Center for Development and Human Rights said in a statement issued on Monday.

The statement added that two other women working in the school were subjected to sexual violence while confronting the raging assailants who also looted and torched the school.

At least 40 churches were attacked, torched and looted in the four days following the security crackdown on the two Cairo protest camps of Islamist supporters of deposed President Mohamed Mursi.

Homes and shops that belong to Egypt's Christian minority were also attacked and looted, in a significant rise of sectarian violence.

The human rights center demanded that the Egyptian police protect civilians from religious extremists, stressing that the assailants should be arrested immediately and that houses of worship should be offered protection.

No photograph was immediately available.