(Reuters) -Nine South African soldiers have been killed in eastern Congo's conflict zone, the South African defence department said on Saturday, as Congolese troops and peacekeepers battled to stop an advance by Rwanda-backed rebels on the city of Goma.

The casualties occurred Thursday when M23 rebels attacked Sake in the eastern DRC, said the DA, which is part of South Africa’s governing coalition.

Fighting has escalated sharply in recent weeks in eastern Congo, where rebels have seized key towns and are closing in on the city of Goma, the government’s last stronghold in the North Kivu province,