Sunday’s warning came as authorities said that the death toll in weekend clashes between Morsi’s backers and security forces near one of the sit-ins had reached 72, in the deadliest single outbreak of violence since the July 3 military coup.

“I assure the people of Egypt that the police are determined to maintain security and safety to their nation and are capable of doing so,” Mohamed Ibrahim told a graduation ceremony at the national police academy.

“We will very decisively deal with any attempt to undermine stability,” said Ibrahim, who is in charge of the police.

In an apparent show of support for the police, a smiling military chief, Abdel Fatah el Sisi, turned up at a graduation ceremony on Sunday broadcast live on state television, receiving a standing ovation from the recruits.

Interior Minister Mohamed Ibrahim hailed him as “Egypt’s devoted son”.

Al Jazeera’s Hoda Abdel Hamid, reporting from Cairo, said his comments come off the back of events over the past week, beginning with the “popular mandate” given to the army to “fight terrorism”.

“By association, the police also got the same mandate. We’ve already seen them co-operating on the ground, and we’ve already heard they will be co-operating together in the coming days.”

However, in one of the first signs of doubt from within the interim cabinet installed after the military takeover, Deputy Prime Minister for Economic Affairs Ziad Bahaa El-Din said the government must not copy the “oppressive and exclusionary policies” of its foes.

“Our position must remain fixed on the need to provide legal guarantees not only for the members of the Brotherhood, but for every Egyptian citizen. Excessive force is not permitted,” El-Din wrote on Facebook.

And in another sign of unease, the Tamarud youth protest movement, which mobilised millions of people against Morsi and has fully backed the army, expressed alarm at an announcement that the interior minister was reviving the feared secret political police shut down after Mubarak was toppled.

Sporadic clashes

Earlier on Sunday, supporters of Morsi pledged to press ahead with their protests, a day after the bloody clashes at in Cairo.

Sporadic violence was also reported nationwide overnight, including in the Suez Canal city of Port Said, where two people were killed.

Gehad El-Haddad, a spokesman for the Muslim Brotherhood, said demonstrators were angry but “hugely defiant” after Saturday’s deaths.

“There are feelings of agony and anger, but also a very strong feeling of determination,” he said.

“People are hugely defiant,” he added.

“For us, if we die, we meet our creator and we did so for a just cause… Either we die or we succeed.”

Officials from Morsi’s Muslim Brotherhood and their allies decried what they called a new “massacre” against their side, only weeks after July 8 clashes with army troops in Cairo that left more than 50 Morsi supporters dead.

The UN’s human rights chief Navi Pillay issued also condemned the violence.

In a Sunday statement, she said: “Despite all the warnings, all the calls for restraint, more than 150 Egyptians have died during protests over the past month, not just in Cairo but in other cities as well,” she said.

“I fear for the future of Egypt if the military and other security forces, as well as some demonstrators, continue to take such a confrontational and aggressive approach. Supporters of the Muslim Brotherhood have the right to protest peacefully like anyone else.”

Pillay called for a “credible, independent investigation” into the killings and punishment for those responsible.

“Given what has happened in recent days, further protests are inevitable, and the onus is clearly on both the security forces and the protesters to ensure there is no repetition of yesterday’s terrible and deeply tragic events.”

Neither side in the Egyptian conflict, however, has shown much taste for reconciliation.