Up to 400 armed South African soldiers have been deployed to the Central African Republic (CAR) by President Jacob Zuma in a bid to help the country's army as it faces threats from rebel groups.

Zuma's office issued a statement on Sunday saying the decision to send soldiers to the CAR is part of South Africa's efforts "to bring about peace and stability in the region".

Several neighbouring countries have sent soldiers to prevent rebels from reaching Bangui, a city of 700,000.

Chad has sent hundreds of forces who are fortifying the road to the capital, while Cameroon, Gabon and Republic of Congo have already sent an estimated 120 troops each.

Zuma's statement also said the South African National Defence Force troops would "assist with capacity building of the CAR Defence Force and will also assist CAR with the planning and implementation of the disarmament, demobilization and re-integration processes" to deal with the country's rebels.

The rebels had pledged to halt their advance pending peace talks in Gabon that are due to start Tuesday.

However, residents say rebels seized two more towns over the weekend, though they are not en route to the capital.

A dozen towns have come under rebel control since the rebel alliance calling itself Seleka began its offensive on December 10.

Seleka, which comprises three rebel groups, accuses Bangui of failing to honour a 2007 peace deal under which fighters who laid down their weapons were supposed to be paid.

Negotiations between the rebels and the Bozize government are set to begin in Gabon on Tuesday.