Violent clashes have broken out in the Egyptian capital Cairo where defiant supporters of ousted President Mohammed Morsi are staging a sit-in protest.
Running battles are taking place around the Rabaa al-Adawiya mosque, says the BBC's Quentin Sommerville at the scene.
He says there is blood on the streets and it is clear a number of people have died. Medics report at least 16 deaths.
Early on Saturday, Interior Minister Mohammed Ibrahim vowed to end the sit-in at the mosque.
He said local residents had complained about the encampment and that the protest would be "brought to an end soon and in a legal manner".
Overnight, huge rallies were held by supporters and opponents of Mr Morsi.
Many thousands occupied Cairo's Tahrir Square in support of the army, which removed Mr Morsi from office earlier this month.
Army chief Gen Abdel Fattah al-Sisi had urged people to take to the streets to give the military a mandate for its intervention.
Our correspondent says automatic gunfire can still be heard and the area around the mosque is being hit by barrages of tear gas.
Security forces, joined by anti-Morsi demonstrators, appear to be forcing protesters closer to the mosque and ambulances are taking people to nearby hospitals, he adds.
Most wounds appear to be from buckshot and CS gas canisters, he says, but there are reports of live fire.Continue reading the main story
There are conflicting reports of the number of deaths.
A doctor in a field hospital at the scene told the Associated Press news agency that at least 16 Morsi supporters had been killed, although the agency later reported the number had risen to 38.
The Muslim Brotherhood - which backs Mr Morsi - told Reuters that 31 people had died.
Brotherhood spokesman Gehad el-Haddad told Reuters: "They are not shooting to wound, they are shooting to kill."
There has also been violence in Egypt's second city of Alexandria, where at least five people were killed late on Friday in clashes between rival factions, state media reported.Morsi charged
Since Mr Morsi, the country's first democratically elected president, was ousted on 3 July, dozens of people have died in violent protests.
Mr Morsi has now been formally accused of conspiring with the Palestinian militant group Hamas, which governs the Gaza Strip and has strong links with the Muslim Brotherhood.
He is alleged to have plotted attacks on jails in the 2011 uprising that overthrew President Hosni Mubarak.
Mr Morsi and several Muslim Brotherhood leaders were freed during a breakout at a Cairo prison in January 2011.
Mr Morsi is to be questioned for an initial 15-day period, a judicial order said.
The order issued on Friday was the first official statement on Mr Morsi's legal status since he was overthrown and placed in custody at an undisclosed location.