Egypt unrest: Morsi marchers die as army fires
Egyptian troops have opened fire on protesters marching in support of ousted President Mohammed Morsi, killing three and wounding dozens.
The shooting came as crowds moved to the Republican Guard headquarters, where Mr Morsi is believed to be held.
Later the Muslim Brotherhood's leader told supporters that protests would continue until Mr Morsi was reinstated.
The army, which removed Mr Morsi on Wednesday after days of unrest, denied shooting live rounds at demonstrators.
However the BBC's Jeremy Bowen at the scene says he saw soldiers fire on the protesters.
About 2,000 people had marched on the officers' club of the Republican Guard after passionate Friday Prayers at the nearby Rabaa al-Adawiya Mosque.
As the crowd grew, got angrier and pushed forward, the troops opened fire - first into the air, then at the crowd, our correspondent reports.
One man fell to the ground with blood on his clothes, says our correspondent - who was himself lightly wounded in the head by shotgun pellets.
Three people were killed and 69 injured in the shooting, the head of Cairo's emergency services said.
By evening, tens of thousands of Muslim Brotherhood supporters had massed outside Rabaa al-Adawiya Mosque and filled 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."
Mr Badie also denied reports that he had been arrested earlier this week. Two other top Brotherhood figures Saad el-Katatni and Mohammed Bayoumi were released on Friday, the state-run Mena news agency reported.
Later supporters and opponents of Mr Morsi clashed in the capital's Tahrir Square.
The Tamarod [Rebel] movement - which organised recent anti-Morsi protests - had urged supporters to mobilise again to "protect the revolution".
Tamarod accuses Mr Morsi and the Muslim Brotherhood - to which he belongs - of pursuing an Islamist agenda against the wishes of the majority, and of failing to tackle economic problems.
There were clashes in other parts of Egypt on Friday too.
In Qina in the south, troops opened fire on pro-Morsi activists trying to storm a security building. At least two people were injured.
Firing was also reported in Alexandria in the north, Egypt's second-largest city, and in the canal city of Ismailiya.
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.
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Muslim Brotherhood spokesman Gehad al-Haddad said the movement was refusing to co-operate with the new leadership and demanded the immediate release of those detained.
UK Foreign Secretary William Hague tweeted that he was "very concerned by reports of deaths in Cairo".
Mr Morsi, Egypt's first freely elected leader, is in detention, as are some senior figures in the Brotherhood. Arrest warrants have been issued for some 300 others.
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.
Mr Morsi's removal followed several days of unrest in which dozens of people died.
Earlier on Friday, unidentified gunmen killed two Egyptian soldier in the northern Sinai town of Al-Arish.
The Sinai has seen a series of militant attacks over the past two years, and it is unclear whether the latest attacks are linked to the political upheaval.