A key peace deal to resolve the conflict in the Central African Republic (CAR) is at risk of collapsing less than a month after it was agreed, news agency AFP reports.

Three militia groups which were among the 14 armed groups that signed the Khartoum Agreement with President Faustin-Archange Touadera, disagreed with the make-up of the new government announced on Sunday.

The Democratic Front of the Central African People (FPDC) said it had, "resolved purely and simply to withdraw from the peace process", adding that the government was "far from being inclusive".

Another large militia, the Patriotic Movement for Central Africa (MPC), citing the same reason, said it considered the accord was "void".

The militias were not happy that the central government held onto sensitive key posts, while six of the 14 armed groups obtained no post at all, AFP reports.

CAR has been unstable since its independence from France in 1960.

It was plunged into turmoil in 2013 when mainly Muslim rebels from the Seleka umbrella group seized power in the majority Christian country. A band of mostly Christian militias, called the anti-Balaka, rose up to counter Seleka.

Seleka handed power to a transitional government in 2014 under international pressure but months of violence followed and the country was effectively partitioned, in spite of the presence of a UN peacekeeping force and a French mission.

The country is undergoing an internationally supervised transition involving a constitutional referendum as well as presidential and parliamentary elections.