CAIRO - AFP/Reuters - Supporters and opponents of Egyptian Islamist President Mohamed Mursi took to the streets on Friday for rival protests a year after his election, as clashes in Alexandria raised fears of widespread unrest.Fervent displays of emotion on both sides underline the bitter divisions in Egypt, with Mursi's opponents accusing him of hijacking the revolution and his supporters vowing to defend his legitimacy to the end. Violence between Mursi supporters and opponents in Egypt's second city of Alexandria injured at least 10 people, a security official told AFP. Television footage showed protesters running in several directions in Alexandria's Sidi Gaber area as gunshots were heard. At least four people have died since Wednesday in clashes in the Nile Delta - three in the city of Mansura and one in Zagazig, medics said.Overnight violence erupted in the eastern part of the Nile Delta, north of the capital, Mursi's own home province of Sharqiya. The unrest is seen by many as a prelude to mass anti-Mursi protests planned for Sunday. In Cairo, thousands of Islamists gathered under the slogan "legitimacy is a red line", in reference to Mursi's insistence that he has a popular mandate. "People must go with everything they've got to defend legitimacy and Egypt," one speaker told the cheering crowd, but also urging them to keep their protests peaceful. Meanwhile, anti-Mursi protesters joined hundreds camped overnight in Tahrir Square, epicentre of the 2011 revolt that toppled Hosni Mubarak and catapulted Mursi to the presidency.Thousands more anti-Mursi protesters demonstrated across Cairo including in the Shubra, Sayeda Zeinab and Mohandesseen districts. Outside the capital, his opponents gathered in Alexandria, Mansura and the canal city of Port Said.The June 30 protest was called by Tamarod (Arabic for Rebellion), a grassroots movement which says it has more than 15 million signatures for a petition demanding Mursi's resignation and a snap election. The broad-based opposition alleges that Mursi reneged on his promise to be a president for all Egyptians and has failed to deliver on the uprising's aspirations for freedom and social justice.Germany warned that Egypt's fledgling democracy faces a "moment of truth", and urged Mursi to implement reforms.Foreign Minister Guido Westerwelle said demonstrators had a right to peaceful assembly, but urged both sides to avoid bloodshed. Westerwelle "is deeply concerned about the current escalation in political tensions in Egypt," his spokesman told reporters. "This is in his view a key moment of truth for political change in Egypt." Mursi himself warned in a televised speech on Wednesday that the growing polarisation threatens to "paralyse" the country. He pledged to consider constitutional reforms and appealed to the opposition to join talks. It was his latest attempt to strike up a dialogue between political factions in a country deeply split between his Islamist allies and an opposition of leftists, liberals, Christians and some Muslim groups. Late on Thursday, however, the opposition National Salvation Front coalition rejected his offer of talks and renewed its call for a snap presidential election.Since taking office last June 30, Mursi has squared off against the judiciary, media, police and even artists. But he has also admitted to failings and vowed to correct them. "I have made many mistakes, there is no question. Mistakes can happen, but they need to be corrected," he said.

Meanwhile, Egypt's leading religious authority warned of "civil war" on Friday and called for calm after a member of the ruling Muslim Brotherhood was killed ahead of mass rallies aimed at forcing the president to quit."Vigilance is required to ensure we do not slide into civil war," the Al-Azhar institute said. In a statement broadly supportive of Islamist head of state Mohamed Mursi, it blamed "criminal gangs" who besieged mosques for street violence which the Brotherhood said has killed five supporters in a week."I came to support the legitimate order," said Ahmed al-Maghrabi, 37, a shopkeeper from the Nile Delta city of Mansoura whose hand bore grazes from street fighting there this week. "I am with the elected president. He needs to see out his term."There was a mostly festive atmosphere in the hot sunshine, with vendors selling mango and cakes and banners flying. Some opposition gatherings were also under way. A handful of protesters watched security men ringing the presidential palace, the focus for Sunday's Cairo rally. Mursi has moved elsewhere.