CAIRO (Reuters) - At least 17 people died across Egypt on Friday as Islamists opposed to the overthrow of President Mohamed Mursi took to the streets to vent their fury at what they say was a military coup.
Five of the confirmed dead were in Cairo, security sources and state television said, and pro- and anti-Mursi protesters clashed in running street battles after dark, while armoured personnel carriers sped between them on a bridge close to the city's historic Egyptian Museum.
Five police officers were gunned down in separate incidents in the North Sinai town of El Arish, and while it was not clear whether the attacks were linked to Mursi's ouster, hardline Islamists there have vowed to take up arms in protest.
In the Mediterranean city of Alexandria, one person was killed in sometimes fierce clashes between rival factions, and in the southern city of Assiut at least one more person died from gunshot wounds.
Tens of thousands of people marched across the country in what Mursi's Muslim Brotherhood movement called a "Friday of Rage" to protest against his ouster and an interim government set up to prepare for new elections.
Egypt's first freely elected president was toppled on Wednesday, the latest twist in a tumultuous two years since the fall of Hosni Mubarak in "Arab Spring" uprisings that swept the region in 2011.
Friday's fatalities add to the dozens of deaths in a month of unrest during which huge rallies in Cairo and other cities called for Mursi's resignation, amid anger over economic stagnation and perceptions of a Brotherhood power grab.
His overthrow was greeted with wild scenes of celebration involving millions of people, but infuriated supporters who fear a return to the suppression of Islamists they endured under generations of military rule.
It has also deepened Egypt's crisis. With its supporters enraged by Mursi's removal from power, the Brotherhood says it wants nothing to do with what the army has billed as an inclusive transition plan, culminating in fresh elections.
The military has provided scarce details - its roadmap gave no timeframe for a new ballot - adding to political uncertainty at a time when many Egyptians fear violence could worsen in an increasingly polarised society.
In an early incident that raised tensions in Cairo, three protesters were shot dead outside the Republican Guard barracks where the deposed Mursi is being held, security sources said.
Mohamed Ezzat, 35, who said he was a Brotherhood member, said protesters would stage a sit-in outside the Republican Guard headquarters and other locations throughout Cairo, to protest the "coup" against Mursi.
"The most important thing with the army is that they stay out of politics. We had a legitimate, elected president, and the army came and removed him," he said.
The army denied blame for the shootings. An army spokesman said troops did not open fire on the demonstrators and soldiers used blank rounds and teargas to control the crowd.
It was unclear whether security forces units other than army troops were also present.
Later, tens of thousands of cheering Islamists gathered near a mosque in a Cairo suburb where they were addressed by Brotherhood leader Mohamed Badie, free to speak despite reports on Thursday that he had been arrested.
In a fiery speech, he vowed to "complete the revolution", and repeatedly referred to Mursi as the president.
"There cannot be a concession on our President Mohamed Mursi, otherwise it is our lives," he shouted as a military helicopter hovered low overhead.
As darkness fell, thousands of pro- and anti-Mursi demonstrators gathered in several parts of Cairo.
Soldiers and special forces backed by armoured personnel carriers attempted to keep the two factions apart, but were not always successful. Several dozen people were injured.
As midnight approached, tensions appeared to have eased.
Islamists also took to the streets of Alexandria and Assiut to join the protests, and in Damanhour, capital of Beheira province in the Nile Delta, 21 people were wounded in violence between supporters and opponents of Mursi.
In the Suez city of Ismailia, soldiers fired into the air as Mursi supporters tried to break into the governor's office. The Islamists retreated and there were no casualties.
State television and radio also reported clashes in the Nile Delta towns of Gharbeya and Beheira, in Qena south of Cairo and the rural province of Fayoum.
In the Sinai Peninsula bordering Israel, where Egypt has struggled to control security since Mubarak was toppled, five police officers were gunned down in two separate attacks in the town of El Arish, medical sources said.
Hardline Islamist groups have exploited a collapse in state authority after the uprising to launch attacks into Israel and on Egyptian targets.
In a video that appeared on YouTube on July 3, the day Mursi was ousted, hundreds of men at a rally in North Sinai province cheered and chanted: "No longer peaceful after today!"
"We heroes, we mujahideen, we tell the Egyptian army, there may come a day when we tell you to get out of North Sinai," one man shouted.
An army spokesman said the army in the Sinai was "on alert". He denied an earlier report by state-owned media Al-Ahram that a state of emergency had been imposed in the South Sinai and Suez provinces, which had caused a spike in oil prices from international markets on edge over the unrest.
Continued violence will alarm the United States. Washington has so far avoided referring to the army's removal of Mursi as a "coup", a word that under U.S. law would require a halt to its $1.5 billion in annual aid.
The top U.S. military officer, General Martin Dempsey, spoke to the chief of staff of Egypt's armed forces on Friday, although no details of what they discussed were provided.
Mursi's opponents also say it was not a coup but an intervention to impose the "people's will".
The African Union voted to suspend Egypt from all its activities in reaction to Mursi's overthrow "until the restoration of constitutional order".
Egypt's interim head of state, Adli Mansour, appointed on Thursday, began work to prepare the country for new elections, dissolving parliament by decree. State television also said he appointed Mohamed Ahmed Farid as head of intelligence.
Foreign diplomacy was being handled by the head of Egypt's armed forces on Friday, as General Abdel Fattah al-Sisi, who announced Mursi's overthrow on Wednesday, called Saudi King Abdullah to reassure him Egypt was stable.
Reporting by Asma Alsharif, Mike Collett-White, Alexander Dziadosz, Seham El-Oraby, Shaimaa Fayed, Maggie Fick, Alastair Macdonald, Shadia Nasralla, Tom Perry, Yasmine Saleh, Paul Taylor, and Patrick Werr in Cairo, Abdelrahman Youssef in Alexandria and Yursi Mohamed in Ismailia; Writing by Mike Collett-White; Editing by Michael Roddy