The attack, which took place in the village of Zawyat Abu Musalam, has heightened fears of sectarian violence, Ahram Online reported Tuesday.
The mob gathered outside a Shiite house, beat the four people inside and then set the house on fire Sunday, police said.
Egypt's ultraconservative Salafists have been accused of fueling anti-Shiite sentiment that led to the attack.
Shiite leaders are expected to hold a news conference to discuss the killings Wednesday, the head of the Misr el-Fatimiya Human Rights Center said.
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