Rebels in the Central African Republic claim to have seized the presidential palace as fighting intensified in the capital Bangui. It comes as former colonial power France called for an emergency meeting at the United Nations on the deteriorating situation.
Fighters in the Séléka rebel coalition advanced into Bangui after the collapse of a two month-old peace deal drawn out with the government of President François Bozizé.
"We have taken the presidential palace. Bozize was not there," one of the rebel commanders on the ground, Colonel Djouma Narkoyo, told news agency AFP.
He said the rebels were planning to move on to the national radio station where rebel leader Michel Djotodia planned to make an address.
"Today will be decisive," Narkoyo said. "We call on our brothers in FACA (the Central African army) to lay down their arms."
Bozize, who himself led a coup in the landlocked country in 2003, has not been seen since his return from South Africa on Friday and there was no statements from the government Sunday about the latest developments.
There are reports he has fled to neighbouring Democratic Republic of Congo.
Witnesses told news agencies there were heavy gun battles across Bangui city centre since early Sunday morning.
Gunfire and explosions in Bangui on Saturday saw the streets emptied as local people fled to their homes.
Narkoyo had told AFP on Saturday the rebels were ready to meet with regional African leaders on the crisis, but refused to negotiate with Bozize.
And he warned that if Séléka - a loose alliance of three rebel movements - captured Bangui, it would set up a new government.
A spokesman for Prime Minister Nicolas Tiangaye on Saturday called on the rebels to accept talks to "avoid a bloodbath".
Tiangaye, an opposition figure, was only appointed as part of the peace deal brokered between the government and the rebels in January, an agreement that broke down last week.
Paris-based rebel spokesman Eric Massi has said the rebel leadership was urging its forces on the ground to refrain from "looting or score-settling with the local population".
France had not issued an evacuation order, but the estimated 1,250 French nationals in the country were advised to stay at home, said Romain Nadal, a spokesman for French President François Hollande.
There were no immediate plans to send reinforcements to back up the 250 French troops in the country to protect them, he added.
The UN Security Council on Friday voiced strong concern about the rebel advances "and their humanitarian consequences" amid reports of widespread summary executions, rapes, torture and the use of children in conflict.