President Mohamed Morsi has ordered Egypt's army from Monday to take on police powers -- including the right to arrest civilians -- in the run-up to a divisive constitutional referendum that has triggered mass street protests.
The decree, published in the government gazette, takes effect on the eve of mass rival protests on the referendum and follows street clashes that have left seven people dead and hundreds injured.
It orders the military to fully cooperate with police "to preserve security and protect vital state institutions for a temporary period, up to the announcement of the results from the referendum," according to a copy of the decree obtained by AFP.
The military, which ruled Egypt between the ouster of former president Hosni Mubarak in February 2011 and the election of Morsi in June this year, has sought to remain neutral in the political crisis.
It has warned it "will not allow" the situation to deteriorate, and urged both sides to dialogue.
Army tanks and troops have since Thursday deployed around Morsi's presidential palace but they have not confronted thousands of protesters who have gathered there every night.
The opposition, made up of secular, liberal, leftwing and Christian groups, has said it will escalate its protests to scupper the referendum.
It views the draft constitution, largely drafted by Morsi's Islamist allies, as undermining human rights, the rights of women, religious minorities, and curtailing the independence of the judiciary.
Morsi, though, has defiantly pushed on with the new charter, seeing it as necessary to secure democratic reform in the wake of Mubarak's 30-year autocratic rule.
Late Sunday, the main opposition group, the National Salvation Front, called for huge protests in Cairo to reject the December 15 referendum.
It dismissed a key concession Morsi made rescinding another decree giving himself near-absolute powers as too late, saying he had already used it to railroad through the draft constitution.
"We do not recognise the draft constitution because it does not represent the Egyptian people," National Salvation Front spokesman Sameh Ashour told a news conference.
Going ahead with the referendum "in this explosive situation with the threat of the Brothers' militias amounts to the regime abandoning its responsibilities," he said.
In recent days, the protesters have hardened their slogans, going beyond criticism of the decree and the referendum to demand Morsi's ouster.
The Muslim Brotherhood, from which Morsi hails, shot back that it and allied Islamist movements would counter with their own big rallies in the capital in support of the referendum.
"We are calling for a demonstration Tuesday, under the slogan 'Yes to legitimacy'," the Brotherhood's spokesman, Mahmud Ghozlan, said.
Morsi's camp argues it is up to the people to accept or reject the draft constitution.
If the charter is rejected, Morsi has promised to have a new one drawn up by 100 officials chosen directly by the public rather than appointed by the Islamist-dominated parliament.
But analysts said still-strong public support for Morsi, and the Brotherhood's proven ability to mobilise the grassroots level, would likely help the draft constitution be adopted.
"The Muslim Brotherhood believes that it has majority support so it can win the constitutional referendum," said Eric Trager, analyst at the Washington Institute for Near East Policy.
If that happens, he warned, it would "set up the country for prolonged instability".