South Africa's government on Tuesday faced calls for an inquiry into why troops were sent to the Central African Republic, after 13 soldiers died there in weekend clashes with rebels who seized the country.

The killings, South Africa's heaviest military loss since apartheid, raised questions over why the South African National Defence Force (SANDF) was present in Bangui -- the official line being they were sent to train local forces.

The main opposition Democratic Alliance said the "highly questionable deployment" should be probed by parliament.

"The real fact is we don't know why the SANDF were deployed in the CAR and that's why we need a comprehensive investigation," said DA defence shadow minister David Maynier.

He added there was speculation the soldiers were sent to "support or prop up" president Francois Bozize, who has now fled Central Africa into exile.

President Jacob Zuma in January authorised the deployment to help local troops as part of a bilateral pact.

Four hundred soldiers were cleared to go but just over 200 were sent.

At the time, the defence force said the soldiers would also protect a small group of South African troops already on the ground.

South Africa has forces in African hotspots like Sudan, and Zuma said Monday the deployment was part of efforts to bring peace to the region.

But Maynier said the probe should aim to determine whether Zuma had misled lawmakers as to the reasons why the troops were sent to Bangui.

The South African soldiers fought a nine-hour battle at the weekend with rebels who swept into the capital Bangui. Altogether, 13 were killed and 27 injured.

The Beeld newspaper, citing sources, reported that the rebels from the Seleka coalition were angry with South Africans soldiers for helping Bozize flee.

The bodies of the dead soldiers arrived home on Tuesday night.

The DA has called for a parliamentary committee to be set up to probe the matter.