Rebels fighting the government in the Central African Republic (CAR) have signed a formal ceasefire following talks in Gabon, reports say.

The rebels and President Francois Bozize agreed to the formation of a unity government from Saturday, Reuters reported.

The Seleka rebel alliance took control of northern and eastern CAR in a four-week offensive starting on December 10.

They have accused Bozize of breaking previous peace deals.

The rebels said they wanted the departure of South African troops and the release of political prisoners in return for the truce.

Earlier, rebel spokesman Florian Ndjadder said: "We are going to agree in principle to a one-week ceasefire."

He said the ceasefire would allow the rebels to "test the goodwill" of President Bozize.

The rebels, who have previously demanded the president's resignation, also said they wanted a new prime minister to be nominated from the opposition, and posted further demands.

"The mercenaries from South Africa must leave Central African territory, [and] the political prisoners must be freed without conditions during the same period," Mr Ndjadder said.

South Africa has begun sending some 400 troops to help stabilise CAR. Forces from neighbouring countries have also been sent.

Both the US and France, the former colonial power, have turned down government pleas for help against the rebels.

The rebels only halted their advance 100km (60 miles) from Bangui after the regional peacekeeping force was deployed.

It is the biggest threat Mr Bozize has faced since he took power in a coup in 2003.

CAR is one of the poorest countries in Africa, despite its considerable mineral resources.