Egypt clashes after army fire kills Morsi supporters
More than 30 people were killed and more than 1,000 injured in Friday's violence following the ousting of Egypt's President Mohammed Morsi, it has emerged.
At least 12 died in Alexandria, and eight in two separate clashes in Cairo, the Health Ministry said.
The army removed Mr Morsi from power on Wednesday after millions of people protested over his leadership.
Mr Morsi, Egypt's first freely elected leader, is in detention.
Some senior figures of his Muslim Brotherhood movement have also been held.
Early on Saturday, state media reported the Brotherhood's deputy leader Khairat el-Shater had been arrested at his Cairo home on suspicion of incitement to violence.
The Tamarod [Rebel] movement - which organised recent anti-Morsi protests - accused the ousted president of pursuing an Islamist agenda against the wishes of most Egyptians, and of failing to tackle economic problems.
The US State Department issued a condemnation of Friday's violence and called for all leaders to put a stop to any further aggression.
UN Secretary General Ban Ki-moon has also expressed alarm at the violence, saying that it was for the people of Egypt to determine the way forward - and all people, including women, needed to be part of that process.
He referred to "horrifying reports of sexual violence".
In a separate development, former president Hosni Mubarak appeared in court on charges of corruption and involvement in the deaths of protesters during the 2011 revolution that ousted him and ultimately brought Mr Morsi to power.
The trial was adjourned until 17 August.
Anger and passion
Most of those killed during fighting in the Mediterranean city of Alexandria, died from gunshot wounds, said Amr Nasr, head of emergency services in the city.
He told the official Mena news agency that 200 people were injured during clashes in Egypt's second-largest city.
Earlier, after midday prayers, Islamist supporters of Mr Morsi staged a series of marches across Cairo - including outside Rabaa al-Adawiya Mosque where tens of thousands massed.
Tensions escalated when a crowd advanced on the nearby headquarters of the Republican Guard, where Mr Morsi is believed to be held.
Troops then opened fire on crowds. Four people were killed and dozens wounded, including the BBC's Jeremy Bowen whose head was grazed by shotgun pellets.
In the evening, tens of thousands of supporters of the Muslim Brotherhood filled the square near the mosque, as well as nearby streets.
The Brotherhood's supreme leader, Mohammed Badie, told the crowd: "We shall stay in the squares until we bring President Morsi back to power."
He said their protests would remain peaceful and called on the army not to "direct your arms against us".
Shortly afterwards, Brotherhood supporters surged across the 6th October Bridge over the Nile river, towards Tahrir Square where anti-Morsi protesters were gathered.
The rival groups hurled fireworks and stones at each other. A car was set on fire and stones and fireworks were thrown. Four people were killed in the clashes.
The BBC's Kevin Connolly in Cairo says there is anger and passion on both sides - as well as a determination to win a battle for the streets which is making the capital a dangerous and volatile place.
Late on Friday, tanks arrived at the bridge to separate the clashing protesters and the violence died down.
There were clashes in other parts of Egypt on Friday.
Islamist attacks on the Sinai peninsula left five police and one soldier dead, security officials said.
The Health Ministry said one protester was killed in the central city of Assiut, and one in Suez. Another three people died in the Suez Canal city of Ismailiya.
In Qina in the south, troops opened fire on pro-Morsi activists trying to storm a security building. At least two people were injured.
Ahead of Friday's protests, the army command said it would not take "arbitrary measures against any faction or political current" and would guarantee the right to protest, as long as demonstrations did not threaten national security.
"Peaceful protest and freedom of expression are rights guaranteed to everyone, which Egyptians have earned as one of the most important gains of their glorious revolution," it said.
On Thursday the head of Egypt's constitutional court, Adly Mahmud Mansour, was sworn in as interim head of state, and he promised to hold elections soon.
On Friday Mr Mansour dissolved the upper house - or Shura Council - which had been dominated by Morsi supporters and had served as sole legislative body after the lower house was dissolved last year.
Mr Mansour also appointed a new intelligence chief, Mohamed Ahmed Farid.