CAIRO - The Egyptian security forces started breaking up two major sit-ins of ousted Islamist president Mohamed Morsi's supporters in Cairo early Wednesday.

Two members of Egypt's security forces were shot dead while clearing a protest camp, according to state-run MENA news agency.

"There is heavy gunfire all over the place and there are policemen in black seem to be from the Special Forces, while at least 15 people were killed in the process," Xinhua's correspondent at the Rabia al-Adawiya Square reported.

A state of chaos overwhelmed the scene as the police removed the sandbag barriers surrounding the square.

The security forces used loudspeakers to warn the residents around the sit-ins not to leave their buildings or look out of the windows during the operation.

At the Nahda Square sit-in, three people were burnt to death after a gas cylinder exploded in their tents due to the turmoil, said the correspondent.

The security forces there used tear-gas bombs to disperse the protesters, some of whom replied with gunfire.

Meanwhile, the Interior Ministry said in a statement that the security forces "have taken all necessary procedures to disband the two said sit-ins, allowing the sit-inners to safely leave through specific announced exits."

Morsi's loyalists have been holding two major sit-ins at the Rabia al-Adawiya Square and Nahda Square since June 28, days before Morsi's ouster, demanding his reinstatement.