CAIRO - The Egyptian military on Monday assumed joint responsibility with the police for security and protecting state institutions until the results of a Dec. 15 constitutional referendum are announced.

The army took up the task in line with a decree issued Sunday by President Mohammed Morsi. The Islamist leader on Monday also suspended a series of tax hikes announced the previous day on alcohol, cigarettes, and other items.

The presidential edict orders the military and police to jointly maintain security in the run-up to Saturday's vote on the disputed charter, which was hurriedly approved last month by a panel dominated by the president's Islamist allies despite a boycott of the committee's liberal, secular, and Christian members.

The decree also grants the military the right to arrest civilians, but presidential spokesman Yasser Ali said it was nowhere near a declaration of martial law.

"It is merely a measure to extend legal cover for the armed forces while they are used to maintain security," Ali told the Associated Press.

There were no signs of a beefed up military presence outside the presidential palace, the site of fierce street clashes last week, or elsewhere in the capital on Monday.

Still, Morsi's decision to lean on the military to safeguard the vote is widely seen as evidence of just how jittery the government is about the referendum on the draft constitution, which has been at the heart of days of dueling protests by the opposition and Morsi's Muslim Brotherhood backers. The two sides clashed in Cairo last week, leaving at least six people dead and hundreds wounded in the worst violence of the crisis.

Both the opposition and Morsi's supporters have called for mass rallies on Tuesday.

The opposition has rejected the referendum, but has yet to call for a boycott or instead a "no" vote at the polls.

"A decision on whether we call for a boycott of the referendum or campaign for a 'no' vote remains under discussion," Hossam Moanis, a spokesman for the National Salvation Front grouping opposition parties and groups told the AP on Monday. "For now, we reject the referendum as part of our rejection of the draft constitution."

The military last week sent out several tanks and armored vehicles in the vicinity of the presidential palace in Cairo following protests there by tens of thousands of Morsi's critics. It was the first high-profile deployment by the military since it handed power in June to Morsi, Egypt's first freely elected president.