Egypt's interior ministry on Wednesday warned organisers planning a campaign of protests against President Mohamed Morsi on August 24 that it would respond "decisively" to any violence.
The protest leaders insist their campaign will be peaceful but Morsi's Muslim Brotherhood movement accuses them of coordinating with former regime figures to try to unseat the Islamist president.
Police "will decisively and legitimately confront any attempt to storm or attack any public or private installation, detain workers in them or cause chaos," the ministry said in a statement.
One of the organisers, the liberal Mohammed Abu Hamed, said the protests would amount to a peaceful "revolution."
The protesters, who are planning a sit-in near the presidential palace, aim to demand an investigation into the Brotherhood's funding and reject Morsi's interim constitution that took legislative powers away from the military, he said.
The Brotherhood has accused protest organisers of planning unrest in the hope that the military, which took charge of Egypt after president Hosni Mubarak was overthrown in February 2011, would step in again.
Brotherhood officials told AFP that the presence of Abu Hamed and other protest organisers by the side of Egypt's former military ruler Field Marshal Hussein Tantawi at a funeral for slain soldiers had influenced Morsi's decision to sack him.
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"The people they (the protesters) had depended on have been retired," senior Brotherhood official Mahmud Ghozlan told AFP.
Morsi sacked Tantawi and other senior military generals after a militant attack on an army outpost in Sinai killed 16 soldiers on August 5, prompting an unprecedented military campaign in the peninsula which borders Israel and Gaza.
At the slain soldiers' funeral, protesters chanted slogans against the Brotherhood and tried to assault Morsi's Islamist prime minister, Hisham Qandil.
Dina Zakaria, a founder of the Brotherhood's Freedom and Justice Party which Morsi headed before his election, said the president preempted any repeat of the scenario that forced Mubarak to resign.
"They hoped that with chaos, they will do what happened to Mubarak, they hoped some in the military council would help them," she said. "The president has secured the military behind him," with the dismissal of Tantawi and other generals.
A presidential source said the sackings were prompted by the Sinai attack, but specifically linked one dismissal, that of military police chief Hamdi Badeen, to the funeral which Morsi did not attend.
A power struggle with the military ensued after Morsi's inauguration on June 30, culminating in the president taking over Tantawi's powers under an interim constitution.
In the weeks before Morsi's election, the military had assumed the powers of the Islamist-dominated parliament after disbanding it and taken control of the state budget, moves that Morsi has now reversed.