At least 32 people were reportedly killed as security forces started an operation to clear pro-Morsi protesters who have been camped out on the streets of Cairo since the Egyptian president was deposed by the military last month.
On Wednesday morning, live footage from Cairo showed smoke engulfing Nahda square - which was later completely cleared - and there were reports of tear gas and birdshot being used on supporters of the ex-president Mohamed Morsi, who was removed from power on July 3.
The Muslim Brotherhood said at least 30 people had been killed, while state television said at least two police officers have been killed.
State television also said a number of people were arrested in Nasr city for having weapons and gas cylinders.
The Interior Ministry said 200 people have been arrested, including 50 in the Rabaa al Adawiyeh sit-in in Nasr City, and 150 in the Nahda Square sit-in in Giza.
The Interior Ministry also warned in a statement that the forces would deal firmly with protesters acting "irresponsibly" and said it would guarantee safe passage to those who want to leave the sites.
By mid-morning, state television reported that security forces had finished breaking up the sit-in at Nahda Square. Bulldozers were said to have been used to uproot the camps.
The Interior Ministry said security forces have "total control" over Nahda Square, and that "police forces have managed to remove most of the tents" in the area. Security forces had blocked all access to the protest camp.
Al Jazeera's Rawya Rageh, reporting from Cairo, said that "this battle is much bigger than what you're seeing, and the casualties. This is a fight for the future of the country, and something that will determine the course of the Egyptian revolution that has been going on for two years now."
"No one expected this to be an easy operation. It became very clear that both sides were engaged in a battle of wills and a dangerous game of brinkmanship,"
Call to the streets
In response to the security operation, the Muslim Brotherhood has urged Egyptians to take to the streets to "stop a massacre".
"This is not an attempt to disperse, but a bloody attempt to crush all voices of opposition to the military coup," Brotherhood spokesman Gehad al-Haddad said on Twitter.
The organisers of a protest at Rabaa al-Adawiya, where several Brotherhood leaders are staying, "is calling on Egyptians to take to the streets to stop the massacre," Haddad said.
Security forces also stormed Nasr City, and there were reports that snipers opened fire on protesters at Rabaa al-Adawiya square.
Security forces said the snipers are only firing tear gas.
Al Jazeera's D. Parvaz said she was prevented from accessing the sit-in and that "there is absolutely no access to the Rabaa al Adawiyeh sit-in except for police and medical services."
"Pro-Morsi supporters are making calls to their supporters, including those in other governates, to tell them to join the protest," she said.
According to our correspondent, all traffic is blocked in the area.
"Many people are being killed right now ...What we can expect is only worse," said Laila, a member of Egypt's Anti-Coup Alliance, a pro-Morsi group. "What's happening now is a crime against humanity."
The action follows weeks of warnings from the interim leadership that force would possibly used to clear the protesters.
At least one person was killed on Tuesday, and many others injured in clashes between supporters and opponents of Egypt's ousted president.
PHOTO CAPTION
Images from near Nahda Square in Giza show black smoke rising as security forces begin clearing the area
Al-Jazeera