Egypt’s Opposition cried fraud in yesterday’s first round of a divisive referendum on a new constitution, accusing President Mohamed Morsi’s Muslim Brotherhood of rigging votes to adopt the Islamist-backed text.

We will arrest anyone who starts riots

But the National Salvation Front Opposition coalition did not immediately make good on a threat to call a boycott if it perceived violations, instead stepping up an appeal to Egypt’s 51 million voters to reject the draft charter.

The Front’s allegations, which included unsealed ballot envelopes and a judge preventing Christians from voting at one Cairo polling station, underlined the highly charged conditions in which the two-stage referendum was taking place.

Three weeks of anti-Morsi protests and clashes in Cairo last week that killed eight people and injured hundreds failed to prevent the referendum going ahead on the draft, largely shaped by Morsi’s Islamist allies.

To ensure security, some 120,000 troops were reinforcing 130,000 police.

Voting was being staggered across the country yesterday and a week later because many judges were not willing to oversee polling.

In Alexandria, Egypt’s second-biggest city, clashes between stone-throwing mobs erupted on the eve of voting, injuring 23 people, the official MENA news agency reported, after a cleric urged worshippers in his mosque to vote yes in the referendum.

The situation there was calm yesterday, Khaled al-Azazi, spokesman for the regional security authorities, told AFP. “We will arrest anyone who starts riots.”

Morsi cast his ballot at a polling station near the presidential palace in Cairo, state television showed. He made no comment to the media.

The Muslim Brotherhood has thrown its formidable organisational machine behind a campaign in favour of the draft constitution.

The proposed charter “offers rights and stability,” said one Cairo voter backing it, Kassem Abdallah.

It will help “the country return to normal,” agreed another, Ibrahim Mahmoud, a teacher.

But many Opposition voters were especially hostile toward the Brotherhood, which the Front believes wants to usher in strict sharia-style (Islamic) laws.

“I’m voting because I hate the Muslim Brotherhood. It’s very simple. They are liars,” said one voter, Abbas Abdelaziz, a 57-year-old accountant.

Omar Abdel Kader, a 60-year-old teacher, said he was voting no because the text “does not represent all Egyptians”. Sally Rafid, a 28-year-old Christian, said: “There are many things in the constitution people don’t agree on, and it’s not just the articles on religion. I’m voting against it.”

International watchdogs, the UN Human Rights Chief, the US and the EU have expressed reservations about the draft because of loopholes that could be used to weaken human rights, including those of women, and the independence of the judiciary.

Analysts said it was likely – but not certain – the draft constitution would be adopted.

Whatever the outcome, “lasting damage to the civility of Egyptian politics will be the main outcome of the current path Morsi has set Egypt on,” one analyst, Issandr El Amrani, wrote for his think-tank, the European Council on Foreign Relations.

“If the no vote wins, the Morsi presidency will have been fully discredited and the pressure for his resignation will only increase,” he said. “If yes wins, the protest movement is unlikely to die down, (and) may radicalise.”

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