Security forces have arrested eight people in connection with the brutal killing of four Egyptian Shiites in a village south of Cairo, officials said on Tuesday.
"Security efforts have been increased to find the rest of the perpetrators after they fled their homes," a security official told the national MENA news agency.
On Sunday, four Egyptian Shiite Muslims were killed when they were attacked by a hostile mob in the village of Abu Mussalem in the Giza province.
A house where the minority Shiites were meeting was surrounded by residents who told them to get out.
When they refused, a crowd of several hundred people stormed the building and killed four Shiites and injured several others.
The attack came after weeks of toxic anti-Shiite rhetoric in the Egyptian media and from Sunni Islamist leaders.
The office of Islamist President Mohamed Morsi and the cabinet both condemned the attack against "Egyptian citizens" without mentioning the term "Shiite", highlighting criticisms by rights groups of the lack of religious freedom in Egypt.
Shiites are estimated as a tiny fraction of Egypt's population of 84-million, most of them Sunni Muslim. Shiism is dominant in Iraq and Iran, a regional rival to Egypt, Lebanon and the conservative Gulf monarchies.
Sunnis have traditionally opposed Shiism, which teaches that many of the Prophet Mohammed's companions revered by Sunnis were corrupt and usurped power from his rightful successor and cousin, Ali.