CAIRO (AFP) - Egyptian police shot dead 23 supporters of Egypt's ousted president Mohamed Mursi and wounded hundreds more in Cairo early on Saturday, a Muslim Brotherhood leader told AFP.

The Brotherhood's Murad Mohammed Ali said police had fired live rounds at the Islamist demonstrators but the state MENA news agency cited a security official it did not identify as denying any live fire by police.

Mr Mohammed Ali said more than 600 people had been wounded.

There was no immediate word from the emergency services or the health ministry.

Clashes broke out at dawn on the road to the airport, with police firing tear gas at stone-throwing protesters, the state MENA news agency said.

It reported that buckshot was fired but said it was unclear who had fired it.

The bloodshed came as interim interior minister Mohammed Ibrahim said that the military-installed caretaker government would move swiftly to break up the Islamists' protest camp in the Nasr City district of Cairo within "the framework of the law."

"There will be decisions from the prosecutor soon, and this situation will be ended," Mr Ibrahim told satellite television channel Al-Hayat.

It also came as authorities charged the ousted president with murder and formally remanded him in custody for 15 days. He had been held without charge since hours after his ouster by the army on July 3.

Mursi stands accused of the "premeditated murder of some prisoners, officers and soldiers" when he broke out of prison during the 2011 uprising that toppled veteran strongman Hosni Mubarak, MENA said.

The charges came as hundreds of thousands of supporters and opponents of the July 3 coup took to the streets on Friday, sparking fierce clashes in the Mediterranean city of Alexandria that left seven people dead.

Army chief General Abdel Fattah al-Sisi, who orchestrated the coup, had called on Wednesday for a mass show of support for a crackdown on "terrorism".