CAIRO — Crowds of protesters marched on the presidential palace in Cairo on Sunday, registering fresh anger against President Mohammed Morsi’s plan to go ahead with a referendum on an Islamist-backed draft constitution.
Egypt’s opposition leaders said they will keep up protests against Saturday’s referendum, but stopped short of advocating either a boycott or a ‘‘no’’ vote.
With efforts to quell the tensions flagging, Morsi on Sunday issued an order placing security over government institutions in the hands of the military until after the results of referendum. The order also grants soldiers the right to arrest civilians.
In a concession to the opposition on Saturday, Morsi rescinded most of a sweeping Nov. 22 decree that temporarily elevated his decisions above judicial review and prompted tens of thousands of protesters to take to the streets, calling for his downfall.
He also offered a convoluted arrangement for the factions to negotiate constitutional amendments this week that would be added to the charter after the vote.
But, Morsi did not budge on a critical demand: that he postpone the referendum set for Saturday to allow a thorough overhaul of the proposed charter, which liberal groups say has inadequate protection of individual rights and provisions that could someday give Muslim religious authorities new influence.
His decision to deploy the military, which will take effect Monday, has been widely interpreted as imposing martial law.
Some opposition leaders vowed to continue the fight to derail the referendum. “We are against this process from start to finish,’’ said Abdel Ghani, a spokesman of the National Salvation Front, according to Reuters. He called for more street protests on Tuesday.
‘‘We have broken the barrier of fear: A constitution that aborts our rights and freedoms is one that we will bring down today before tomorrow,’’ Mohamed ElBaradei, the former diplomat now acting as coordinator of the secular opposition, wrote on Twitter early Sunday. ‘‘Our power is in our will.’’
In recent days, protesters have attacked more than two dozen Muslim Brotherhood offices and ransacked the group’s headquarters, and more than seven people have died in street fighting between Islamists and their opponents.
The moves over the weekend offered little hope of fully resolving the standoff, in part because opposition leaders had ruled out — even before his concessions were announced — any rushed attempt at a compromise just days before the referendum.
“No mind would accept dialogue at gunpoint,’’ said Mohamed Abu El Ghar, an opposition leader, alluding to previously floated ideas about last-minute talks for constitutional amendments.
Nor did Morsi’s Islamist allies expect his proposals to succeed. Many said they had concluded that much of the secular opposition was primarily interested in obstructing the transition to democracy at all costs, to try to block the Islamists from winning elections.
Instead, some of the president’s supporters privately relished the bind they believed Morsi had built for the opposition by giving in to some demands, forcing their secular opponents to admit they are afraid to take their case to the ballot box.
Soon after the state newspaper Al-Ahram suggested on Saturday the president would impose martial law, a military spokesman read a statement over state television that echoed Morsi’s own speeches.
The military ‘‘realizes its national responsibility for maintaining the supreme interests of the nation and securing and protecting the vital targets, public institutions, and the interests of the innocent citizens,’’ the spokesman said, warning of ‘‘divisions that threaten the State of Egypt.’’
‘‘Dialogue is the best and sole way to reach consensus that achieves the interests of the nation and the citizens,’’ he added. ‘‘Anything other than that puts us in a dark tunnel with drastic consequences, which is something that we will not allow.’’
Morsi’s announcement Saturday about using the military for security marked the steepest escalation yet in the political battle between Egypt’s new Islamist leaders and their secular opponents over the draft constitution.
The president said he issued the Nov. 22 decree that set off the crisis to prevent the Mubarak-era courts from dissolving the constitutional assembly and upending the transition to democracy. The terms of his concession were ill-defined.
The new decree Morsi issued Saturday night said he retained the limited authority to issue ‘‘constitutional declarations’’ protecting the draft charter that judges could not overturn.