CAIRO - Egyptians voted narrowly in favor of a constitution shaped by Islamists but opposed by other groups who fear it will deepen divisions, officials in rival camps said on Sunday after the first round of a two-stage referendum.Next week's second round is likely to give another "yes" vote as it includes districts seen as more sympathetic towards Islamists, analysts say, meaning the constitution would be approved.But a close win, if confirmed, would give Islamist President Mohamed Morsi only limited cause for celebration as it would show a wide rift in a country where he needs to build consensus on tough measures to fix a fragile economy.The Muslim Brotherhood's party, which propelled Morsi to office in a June election, said 56.5 percent backed the text. Official results are not expected till after the next round.Morsi and his backers say the constitution is vital to move Egypt's democratic transition forward. Opponents say the basic law is too Islamist and tramples on minority rights, including those of Christians who make up 10 percent of the population.The build-up to Saturday's vote was marred by deadly protests. Demonstrations erupted when Morsi awarded himself extra powers on November 22 and then fast-tracked the constitution through an assembly dominated by his Islamist allies.However, the vote passed off calmly with long queues in Cairo and several other places, though unofficial tallies indicated turnout was around a third of the 26 million people eligible to vote this time. The vote was staggered because many judges needed to oversee polling staged a boycott in protest.The opposition had said the vote should not have been held given violent protests in the Arab world's most populous nation, which is watched closely from abroad to see how Islamists, long viewed warily in the West, handle themselves in power.Increasingly divided nationAs polls closed, Islamists attacked the offices of the newspaper of the liberal Wafd party, part of the opposition National Salvation Front coalition that pushed for a "no" vote."The referendum was 56.5 percent for the 'yes' vote," a senior official in the Brotherhood's Freedom and Justice Party operations room set up to monitor voting told Reuters.The Brotherhood and its party had representatives at polling stations across the 10 areas, including Cairo, in this round. The official, who asked not to be identified, said the tally was based on counts from more than 99 percent of polling stations."The nation is increasingly divided and the pillars of state are swaying," opposition politician Mohamed ElBaradei wrote on Twitter. "Poverty and illiteracy are fertile grounds for trading with religion. The level of awareness is rising fast."One opposition official also told Reuters the vote appeared to have gone in favor of Islamists who backed the constitution. The opposition initially said its exit polls indicated the "no" camp would win comfortably, but officials changed tack during the night. One opposition official in the early hours of Sunday said it would be "very close". There was no formal statement from the opposition National Salvation Front."Even if this result is correct, that does not mean that this constitution can pass, because it means more than 40 percent of the people didn't agree with it," said Issam Amin, speaking on a Cairo street and echoing the opposition line that the constitution needed consensus backing not a simple majority.A narrow loss could still hearten leftists, socialists, Christians and more liberal-minded Muslims who make up the disparate opposition camp, which has been beaten in two elections since Hosni Mubarak was overthrown last year.They were drawn together to oppose what they saw as Morsi's power grab and his constitution push. The National Salvation Front includes prominent figures such as ElBaradei, former Arab League chief Amr Moussa and firebrand leftist Hamdeen Sabahy.If the constitution is approved, a parliamentary election will follow early next year. Opposition leaders say the Front could help unite the opposition for that poll after their divided ranks have split the vote in previous elections."It's wrong to have a vote or referendum with the country in the state it is - blood and killings, and no security," said Emad Sobhy, a voter who lives in Cairo. "Holding a referendum with the country as it is cannot give you a proper result."