Fighting has broken out between Chadian government and rebel forces close to the north of the capital N'Djamena, according to French media reports.
Rebel forces in Chad say they have entered the outskirts of the capital, Ndjamena, after heavy fighting with government troops.
Heavy weapon fire could be heard in the centre of the city and was apparently getting louder, the reports said.
Heavy weapon fire could be heard in the city centre and seemed to be getting louder, French media reports said.
The fighting came as France and the United States instructed their citizens to go to designated areas of the city to prepare for evacuation.
The fighting came as France and the United States instructed their citizens to go to designated areas of the city to prepare for evacuation.
The African Union has expressed deep concern at the crisis.
The African Union has expressed deep concern at the crisis.
"We are really, deeply preoccupied by the situation today in Chad," said Jean Ping, the newly elected chairman of the AU Commission.
Following clashes on Friday around the city of Massaguet, both sides claimed victory.
On Saturday, a rebel spokesman, Abakar Tollimi, told AFP news agency that government troops were "scattering" and that President Idriss Deby would fall within hours.
Government officials said the forces were evenly matched but have not ruled out the possibility that the rebels could take N'Djamena.
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