South African troops in the Democratic Republic of Congo have suffered their first fatalities since their recent deployment to quell a rebellion.

Two soldiers were killed and three were injured after a mortar bomb landed in their base on Wednesday.

The attack has led to South African opposition politicians calling for the withdrawal of troops from DR Congo.

The troops are part of a regional force helping DR Congo's military as it confronts a series of armed groups.

The most prominent group is the M23, which has taken up positions on the major routes leading into Goma, the main city in the east of DR Congo.

Th M23's advance has resulted in tens of thousands being forced from their homes - adding to the nearly seven million who have fled because of multiple conflicts in the east.

But the South African army has not linked Wednesday's attack to the M23.

In a statement, it says the "details of this incident are still sketchy".

South Africa began deploying troops to eastern DR Congo in December under the banner of the 16-member regional bloc, the Southern African Development Community (Sadc).

They are taking over from the Kenyan-led East African Force (EAF), which left in December - about a year after it was welcomed by President Félix Tshisekedi.

He was re-elected in December for a second term in office - and one of his key campaign promises was to tackle the insecurity that has wracked the east of the country for three decades.

Sadc has acted in the interests of solidarity, as DR Congo is part of the regional grouping..

It previously warned that an attack against one of its members would be met with "immediate collective action", and its troops would help DR Congo's military in "fighting" armed groups.

This view is more in tune with Mr Tshisekedi's - he wants a partner who will tackle the rebels head on.

Mr Tshisekedi booted out the EAF, accusing it of being ineffective and refusing to go on the offensive against the M23.

He has also ordered a UN force, which has been in the country for around 25 years, to leave by the end of 2024 after levelling similar accusations against it.

South Africa is the regional superpower, and will form the backbone of the force.

Mr Tshisekedi is hoping that it will repeat the success it had during a previous deployment. That was more than a decade ago, when the M23 - accused of being backed by Rwanda - also made huge territorial gains in the resource-rich east.

Though then operating under the banner of a UN Intervention Brigade, Sadc troops forced the M23 to retreat. The M23 has since regrouped after a peace deal floundered, and is once again on the offensive.

Remadji Hoinathy, an analyst with the South Africa-headquartered Institute for Security Studies, said the M23 was now stronger and better equipped.

The AFP news agency has quoted a UN document as saying that the Rwandan army is using sophisticated weapons such as surface-to-air missiles to support the M23.

Rwanda has consistently denied backing the rebel group.

Dr Hoinathy said there was no clarity on its strength, but South Africa had a strong and well-equipped army.

Earlier this week, South Africa's President Cyril Ramaphosa said that 2,900 troops were to be deployed, without saying how many were already in DR Congo.

Malawi and Tanzania are also sending soldiers, but have not yet given any details.

South Africa's two biggest opposition parties - the Democratic Alliance (DA) and Economic Freedom Fighters (EFF), are not happy about the deployment and not convinced about the effectiveness of the troops.

At a press conference on Thursday, EFF leader Julius Malema called for the immediate withdrawal of South African soldiers from DR Congo.

"They [South African troops] are sent there to be killed because they are not properly trained," he said.

"We just don't have the army. The ANC has collapsed the army," Mr Malema added, referring to the governing party, the African National Congress (ANC).

DA defence spokesman Kobus Marais said on X, formerly Twitter, that the fatalities were "avoidable", and the government had been warned that the deployment was "irresponsible and unacceptable".

In an earlier statement, he said the troops will be "sitting ducks" because of a lack of airpower.

"Without proper air cover as well as transport and air elements, the SANDF [South African National Defence Force] troops will find it difficult to operate effectively in eastern DR Congo, which is a complex and hostile terrain," Mr Marais added.

Mr Ramaphosa defended the deployment in parliament, saying South Africa was "part of peace-keeping missions all over the world".

"We salute our defence force personnel who brave great dangers to make Africa a more peaceful and stable continent. That is what we applaud them for and we dip our heads for those who are injured and for those who may have fallen," Mr Ramaphosa said.