Egypt witnessed a day of violent clashes between supporters of the Muslim Brotherhood and the police at a level unparalleled in more than two months.
The ministry of health said on Saturday that 14 people were killed and 62 injured in clashes across the country on Friday.
Earlier on Saturday, a medical source had told Al-Ahram 17 people were killed during the clashes.
17 police officers were also injured, according to a senior security source.
Protesters died in Cairo, Alexandria, the Suez Canal city of Ismailia, Fayoum and Minya in Upper Egypt, according to the Egyptian health ministry.
The police said it arrested more than 258 Brotherhood supporters including some possessing explosives and weapons.
Clashes continued into the night east of the capital at Gisr El-Suez Street and at the other end of the city's outskirts at Al-Talbiya area near the pyramids, where burning tires, tear gas and stone throwing painted scenes on Egyptian television channels.
Confrontations took place in many other locations around the capital, but police managed to disperse them more effectively. In Nasr City – which had calmed down amid a heavy police presence, according to Al-Ahram's Arabic news website – a public bus was smashed and several cars were shattered in the violence.
Police fired teargas at a student march at the nearby Al-Azhar University, a major scene of Islamist protests in recent weeks, state news agency MENA said.
Brotherhood supporters set the Faculty of Agriculture building at Al-Azhar University on fire and damaged five administrative offices inside, Al-Ahram reported.
Police also fired teargas on Friday afternoon when some 300 pro-Brotherhood protesters blocked off Cairo's corniche road near the High Administrative Court in the southern suburb of Maadi. Protesters responded with stone-throwing.
Eyewitnesses told Al-Ahram on Friday morning that protesters in the Giza's Faysal district had thrown Molotov cocktails at an armoured police vehicle, setting it on fire, and shot at police officers trying to escape from the car.
Violence also flared in Egypt's second city of Alexandria when hundreds of Islamists clashed with civilian opponents, using stones and birdshot. Security forces stepped in to scatter the crowds, arresting several pro-Brotherhood protesters in possession of "rioting tools" and leaflets against the police and army.
The National Alliance to Support Legitimacy had called for Friday demos in the run-up to their planned boycott of the upcoming constitutional referendum.
Supporters of the Muslim Brotherhood and the group's ousted president Mohamed Morsi reject the new constitution, which was amended after Morsi's ouster.
Recent months have seen regular clashes between protesters and security forces during weekly Friday protests.
Egypt's authorities declared the Brotherhood a terrorist organisation in December, accusing the group of links with recent attacks on state institutions and on churches since Morsi's ouster.
Interior ministry officials have warned that anyone taking part in pro-Brotherhood protests after its designation as a terrorist organisation will be punished with five years in jail, while protest leaders might face the death penalty.
Egypt's interior ministry said in a statement on Friday afternoon it had arrested 120 Brotherhood members nationwide, and said they were armed with explosives, Molotov coctails, firearms and knives.