Islamists backing Egyptian President Mohamed Morsi and the secular opposition ranged against them were Thursday rolling out campaigns over a divisive new constitution that has sparked weeks of protests.
The staggered referendum to decide the text is to begin on Saturday across half of Egypt, including in Cairo and Alexandria. The rest of the country will vote a week later, on December 22.
The protests, and over near-absolute powers that Morsi gave himself for two weeks to push it through, have failed to sway the president from his path.
"It's you who will pay the price if you vote yes. No to the constitution," said an online campaign advertisement by an opposition group called April 6.
The pro-referendum camp has released videos with a song that goes "This constitution is not too bad, it was written by a committee of heroes."
It also has supporters holding "Yes to the constitution" placards along main roads.
Fears of violence remain after violent clashes in Cairo last week in which eight people were killed and more than 600 injured.
Thousands of soldiers and 130,000 police will be deployed on Saturday to provide security, officials told AFP.
Morsi has ordered the army to secure state institutions, giving it powers of arrest until the referendum result is known.
The military, which ruled for 16 months following the ouster of president Hosni Mubarak early last year, has tried in vain to bring both sides together for talks to calm the crisis.
Morsi ordered the referendum to be split because of a lack of judges willing to monitor voting.
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The opposition National Salvation Front, while urging its supporters to vote "no", warned it could yet call a last-minute boycott if the referendum was not brought back to just one day of voting, and if judges and independent observers did not monitor every polling station.
"The Salvation Front will not recognise the results of a referendum that does not occur in conditions of total transparency," it said in a statement, adding that it "deeply feared" that would be lacking.
Mohamed ElBaradei, a former UN nuclear energy agency chief who heads the Front, tweeted: "Insistence on referendum in an explosive, polarized, chaotic & lawless environment is leading country to the brink."
Egyptian citizens were divided over the referendum.
"I'm voting yes," said Mohammed Hassan, a 28-year-old Cairo resident.
"The Muslim Brotherhood is good. No one has given them a chance. They've been in power for five months compared to 30 years for Mubarak," he said.
Hamdi Imam, a street bookseller in his 50s, said: "I'm not going to vote because the constitution has blood on it... The Muslim Brotherhood will destroy the country."
The referendum outcome was uncertain, though many analysts thought it likely to pass, given the Brotherhood's efficiency in mobilising Egypt's vast poorer segment of society.
The opposition sees the proposed charter, drafted by a panel dominated by Islamists, as weakening human and gender rights, bolstering the military and undermining the judiciary's independence.
It fears ambiguities and loopholes in the charter will push Egypt closer to a form of sharia law favoured by the more ultra-orthodox Islamists.
The UN human rights chief, the United States, European nations and international watchdogs have also criticised the draft constitution and the way it was rammed through.