A protest by at least 100,000 Egyptians outside the presidential palace in Cairo has turned violent as tensions grow over Islamist president Mohammed Morsi's seizure of nearly unrestricted powers and a draft constitution hurriedly adopted by his allies.
Crowds around the capital and in the coastal city of Alexandria were still swelling several hours after nightfall. The large turnout signalled sustained momentum for the opposition, which brought out at least 200,000 protesters to Cairo's Tahrir Square a week ago and a comparable number on Friday. They are demanding that Mr Morsi rescind decrees that placed him above judicial oversight.
In a brief outburst, police fired tear gas to stop protesters approaching the palace in the capital's Heliopolis district.
Mr Morsi was in the palace conducting business as usual while the protesters gathered outside. But he left for home through a back door when the crowds "grew bigger", according to a presidential official.The official said Mr Morsi left on the advice of security officials at the palace and to head off "possible dangers" and to calm protesters.
Mr Morsi's spokesman, however, said the president left the palace at the end of his work schedule through the door he routinely uses.
The violence erupted when protesters pushed aside a barricade topped with barbed wire several hundred yards from the palace walls. Police fired tear gas and then retreated. With that barricade removed, protesters moved closer to the palace's walls, with police apparently choosing not to try and push the crowds back.
Soon afterwards, police abandoned the rest of the barricades, allowing the crowds to surge ahead to the walls of the palace complex. But there were no attempts to storm the palace, guarded inside by the army's Republican Guard. The brief outburst of violence left 18 people injured, none seriously, according to the official Mena news agency.
Protesters also commandeered two police vans, climbing atop the armoured vehicles to jubilantly wave Egypt's red, white and black flag and chant against Mr Morsi. Nearly two hours into the demonstration, protesters were mingling freely with the black-clad riot police, with many waving the flag and chanting against Mr Morsi.
There were as many as 100,000 protesters in the immediate vicinity of the palace and the wide thoroughfare that runs by it. Thousands more filled side streets leading off the area.
Many in the crowd were chanting "erhal, erhal", Arabic for "leave, leave" and "the people want to topple the regime" - two well-known chants from the 2010-2011 Arab Spring revolts that toppled Hosni Mubarak and other Middle Eastern and North African rulers.