Rwandan-backed rebels are gaining ground in eastern Congo despite the unilateral ceasefire they declared earlier this week.

Rwandan-backed M23 rebels have seized control of the town of Nyabibwe in eastern Democratic Republic of Congo's South Kivu province, eight sources said on Wednesday - an apparent violation of a unilateral ceasefire they declared this week.

The Eastern Congo rebel alliance that includes the M23 has declared a ceasefire for humanitarian reasons starting on Feb. 4, the group known as the Congo River Alliance said in a statement.

Rwandan-backed armed group M23 announced a humanitarian “ceasefire” from Tuesday in DR Congo’s explosive east, days before a planned crisis meeting between Congolese President Felix Tshisekedi and Rwandan President Paul Kagame.

The U.N. says Rwanda-backed rebels are expanding their presence in eastern Congo after capturing the region's major city.

Over 2,000 bodies require burial in Goma after Rwanda-backed M23 rebels took over the Democratic of Congo city last week, inflaming a decade-old conflict and humanitarian crisis, Congo's communications minister Patrick Muyaya said late on Monday.

The Rwanda-backed rebels who seized a major city in eastern Congo have declared a unilateral ceasefire, citing humanitarian grounds. But, there was no sign of them giving up control of Goma at the heart of a region home to trillions of dollars in mineral wealth.