Several civilians have died, around 1,000 are wounded, and thousands have fled their homes since rebels seized parts of the capital N'Djamena on February 2 and intense fighting broke out with troops.
The rebels are a loose coalition of three opposition groups whose leaders accuse President Idriss Deby of corruption and embezzling millions of dollars in oil revenue. The rebels entered the capital in an attempt to oust Deby, who seized power in 1990.
Media in several Arab countries cited a spokesman for the rebel forces as saying they had given their agreement to an immediate ceasefire due to "the suffering of the Chadian people," and in line with the peace initiatives put forward by the African Union's mediators.
The rebels said they wanted a ceasefire to be followed by a national dialogue with a view to a peaceful resolution of the conflict and the establishment of "a truly democratic political regime" in the oil-rich Central African country.
However, French media cited in their latest reports Chad's prime minister, Nourredine Delwa Kassire Coumakoye, as saying that the insurgency had been quashed and that the remaining rebel forces were fleeing the area around the capital.
"Why a ceasefire? They [the rebels] don't exist any more. With whom would we sign a ceasefire? We've got them under control," Coumakoye told international news channel France 24.
The United Nations Security Council on Monday strongly condemned the rebel attack and authorized France and other nations to help Chad's government. France has around 1,800 troops in the country, its former colony.
Chad gained independence from France in 1960. It borders the war-ravaged Darfur region of Sudan.
On Tuesday, the Russian Foreign Ministry urged the warring sides to end hostilities and prevent the conflict from spreading to neighboring countries.
In April 2006, rebels from the United Front for Change stormed the capital in a similar attempt to oust the authorities, but their attacks were repelled by government forces.
Chadian officials claim that the rebels are supported and armed by neighboring Sudan, but Sudanese authorities have repeatedly denied such allegations.