CAIRO (AP) -- Egypt's military assumed responsibility Monday for protecting state institutions and maintaining security ahead of a Dec. 15 constitutional referendum, as the country braced for another round of mass demonstrations by the supporters of the country's Islamist president and the liberal opposition over the disputed charter.
The referendum on a contentious new constitution lies at the heart of a bitter political battle that has deeply polarized Egypt and triggered some of the worst street violence between backers and opponents of President Mohammed Morsi since he took power in June as the country's first democratically elected leader.
So far, Morsi has stood firm on the referendum, refusing to yield to opposition demands that he scrap the vote scheduled for Saturday. The opposition, meanwhile, was still trying to decide late Monday whether to boycott the referendum or rally Egyptians to vote "no" to the draft constitution, and hoping that a massive turnout for a rally Tuesday would force the president to cancel the balloting.
"We still have a chance, with popular rejection, to stop the referendum," said Basil Adel, a former lawmaker and liberal activist.
Egypt's political crisis began on Nov. 22 when Morsi issued a decree granting himself -- and the Islamist-dominated panel writing the constitution -- immunity from judicial oversight or challenge. Those decrees sparked mass demonstrations, with opponents saying they were issued initially to protect the draft charter from the judiciary.
The constituent assembly then hurriedly approved the draft constitution in a marathon overnight session, further inflaming those who claim that Morsi and his Islamist allies, including the Muslim Brotherhood, are monopolizing power and trying to force their agenda into practice.
That prompted hundreds of thousands of the president's opponents to take to the streets in massive rallies -- the largest from primarily secular groups since the uprising that toppled Hosni Mubarak last year. Morsi's supporters responded with huge demonstrations of their own, which led to clashes in the streets that left at least six people dead and hundreds wounded.
Morsi has rescinded the decree that gave him absolute powers, but did not meet the opposition's main demand and delay the referendum.
With tensions running high in the country, the president on Sunday ordered the military to take responsibility for security and protect state institutions along with the police until the results of the constitutional referendum are announced.
On Monday, the army took up the task in line with the presidential decree, which also grants the military the right to arrest civilians.
Presidential spokesman Yasser Ali tried to downplay concerns the move was a step toward martial law, saying instead that "it is merely a measure to extend legal cover for the armed forces while they are used to maintain security."
There were no signs of an increased military presence outside the presidential palace, where tanks have been deployed since last week's fierce street clashes, or elsewhere in the capital on Monday.
Still, the decision to lean on the military, which had a spotty record over the tumultuous 16 months that it ran Egypt after Mubarak's fall, prompted concern among international rights groups.
"Considering the track record of the army while they were in charge, with more than 120 protesters killed and in excess of 12,000 civilians unfairly tried before military courts, this sets a dangerous precedent," said Hassiba Hadj Sahraoui of Amnesty International.
Human Rights Watch called on Morsi to put limits to military's policing powers to prohibit trials of civilians in front of military tribunals.
Activists and rights groups have documented a catalog of human rights violations by authorities during the period of military rule.
Judges have gone on strike to protest Morsi's decrees, which they perceive as an "assault" on the judiciary, and have said they would not oversee the Dec. 15 vote as is customary for judges in Egypt. Judges of the nation's administrative courts announced Monday they were conditionally lifting their boycott of the vote, but they said their supervision of the process was conditional on bringing an end to the siege of the Supreme Constitutional Court by Morsi's supporters.
In exchange for their supervision, they also demanded assurances that authorities would crack down on vote canvassing outside polling stations and offer life insurance policies to the judges.
Against this backdrop, Morsi on Monday suspended a series of tax hikes announced a day earlier on 50 good and services including alcohol, cigarettes and mobile phones.
The decision to raise the taxes just days ahead of a referendum that has deeply divided the nation baffled many in Egypt.