An Al-Qaeda inspired group said it carried out the assassination on Tuesday of a top Egyptian police general and threatened similar attacks against the army chief and interior minister.
General Mohamed Saeed, an aide to interior minister Mohamed Ibrahim, was gunned down as he left his home in a west Cairo neighbourhood on Tuesday morning.
Claiming responsibility in a statement posted on a jihadist website, Ansar Beit al-Maqdis, or Partisans of Jerusalem, said it carried out the killing.
Addressing Ibrahim and army chief Abdel Fattah al-Sisi, the group warned: "Vengeance is coming."
The interior minister was already the target of an abortive assassination attempt claimed by the group last September in which a bystander was killed.
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Ansar Beit al-Maqdis has claimed most of the deadliest attacks in Egypt since the army's overthrow of Islamist president Mohamed Morsi last July, saying that they were in revenge for a deadly crackdown by the security forces.
Morsi's Muslim Brotherhood, which renounced violence decades ago, has condemned the attacks but that has not stopped it being declared a terrorist organisation by the military-installed authorities.
The blacklisting makes even declarations of verbal support for the Brotherhood punishable by heavy prison sentences.
Ansar Beit al-Maqdis also claimed responsibility for a Monday attack on Egypt's gas export pipeline through the restive Sinai Peninsula to Israel and Jordan.
The attack on the pipeline was the third in less than a month and follows repeated attacks last year that severely disrupted Egypt's gas exports.
The group had previously claimed a car bombing which killed five people outside Cairo police headquarters on Friday.