The Central African Republic's government and the Seleka rebels are holding peace talks in Gabon, but both sides appear to be refusing to back down from the conflict.

The rebels have called on President Francois Bozize to step down and be charged in an international criminal court for alleged war crimes, including "detentions and false imprisonment, kidnappings, disappearances, assassinations and summary executions".

"We're asking for the head of state to go, because he's not been up to his function, and we're asking for transition. We need a transitional government, a transitional assembly," Crepin Mboli Gumba, a member of the opposition party, told Al Jazeera.

The statements came a day after Bozize accused the rebels of being foreign-backed "mercenary terrorists".

The three-way talks between the Central African government, rebels and the political opposition are being brokered by regional bloc the Economic Community of Central African States (ECCAS) in Libreville, the Gabonese capital.

The talks were to focus on renegotiating peace agreements signed by Bangui between 2007 and 2011 which rebels say have been violated.

"I am asking everyone to show restraint and, in this context, we will suggest at the start of the talks that a ceasefire agreement be signed," said Basile Ikouebe, the foreign minister of Congo, which is mediating the talks.

A 'political transition'

Seleka, an umbrella group of several rebel factions, launched an offensive in the north on December 10 and have since seized control over many cities and towns in the country's north.

Bozize has relied on foreign military help to fend off a series of smaller insurgencies. Regional powers, chief among them Chad, have sent in hundreds of troops to bolster his army this time.

The rebels moved southward towards Bangui, the capital, but stopped around 160km from the capital after regional powers sent troops to bolster the government's army.

Nine opposition parties attending the talks also demanded the president step down, accusing him of rigging election victories in 2005 and 2011 and isolating the country.

"The resignation of the President Bozize and the establishment of a political transition is a sine qua non condition to end the crisis," the parties said in the joint statement seen by the Reuters news agency.

They also demanded the suspension of the constitution and the appointment of a transitional government and national assembly for not more than three years, pending elections. Bozize has asked to be allowed to complete his mandate, which ends in 2016, and has promised not to seek another term.