South Africa has sent additional troops and military equipment to Democratic Republic of Congo in recent days, political and diplomatic sources said, after 14 of its soldiers were killed in fighting with Rwanda-backed rebels last month.

The South African reinforcement comes amid fears that fighting in eastern Congo could spark a broader war in a powderkeg region that has over the past three decades witnessed genocide, cross-border conflicts and dozens of uprisings.

Flight data reviewed by Reuters showed transport aircraft flying from South Africa to Lubumbashi, in southern Congo. An airport employee there confirmed that military planes had landed last week.

"We have been informed of a (South African National Defence Force) troop build-up in the area of Lubumbashi. We gather that approximately 700-800 soldiers had been flown to Lubumbashi," Chris Hattingh, a South African lawmaker, wrote in a text message to Reuters.

Hattingh, the defence spokesperson for the Democratic Alliance, a member of the governing coalition, said it was "difficult to figure out what is exactly unfolding" because parliament's defence committee had not been briefed.

The SANDF spokesperson said on Friday he was not aware of the deployment to Lubumbashi and declined to comment further on Monday. A Congolese army spokesperson said he could not confirm or deny the deployment.

Lubumbashi is about 1 500 km (930 miles) south of Goma, the eastern city on Rwanda's border that the M23 rebels seized last month during an offensive that has killed over 2 000 people and displaced hundreds of thousands.

South Africa is believed to have around 3 000 troops deployed in Congo, both as part of a UN peacekeeping mission and a Southern African regional force tasked with helping Congo's army combat the M23 insurgency.

'NOT OUR WAR'
Its intervention has drawn heavy criticism at home after the fall of Goma left South African soldiers surrounded and with no clear exit strategy.

"They're extremely poorly resourced and equipped," said Kobus Marais, who served as the DA's shadow defence minister before the party entered a governing coalition last year. "This is not our war."

Marais, now a defence analyst who said he was being kept abreast of the situation, said the flights to Lubumbashi carried medicine, ammunition and consumables. The additional troops were to assist in the case of further clashes and as a deterrent as negotiations to end the fighting get underway.

An IL-76 cargo plane with the tail number EX-76008 made five round-trip flights from Pretoria to Lubumbashi between January 30 and February 7, according to flight tracking data from FlightRadar24.

The flights left from the south side of Pretoria, where the South African air force has a base.

An employee in Lubumbashi airport told Reuters on Saturday that he had seen several rotations of aircraft bringing troops and equipment. Three diplomats and a minister from a country in the region said they were aware of the deployment.

With M23 rebels controlling Goma's airport, South African troops there are cut off from resupplies.

"The pattern of chartered cargo flights under SANDF callsigns from South Africa to both Lubumbashi and locations inside (neighbouring) Burundi points to the likely creation of some type of additional contingency force," said a defence expert who asked not to be named.

Two successive wars in the 1990s and 2000s grew out of the Rwandan genocide, drawing in a half dozen of Congo's neighbours and killing millions, mainly through hunger and disease.

Uganda and Burundi, which already have thousands of troops in eastern Congo, are also reinforcing their positions.

Rwanda rejects accusations that thousands of its troops are fighting alongside M23, while African leaders have urged the parties to hold talks.