Nearly three thousand people have been killed in the city of Goma in the eastern Democratic Republic of Congo, according to the United Nations, after the provincial capital was captured by rebels following days of fierce fighting with the Congolese army.

Goma remains “under occupation” by Congo’s M23 rebels and the ceasefire they announced has been broken as their forces engage in heavy fighting along the main route to South Kivu’s main city Bukavu.

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

The rebels said the ceasefire would start Tuesday. The announcement came shortly after the U.N. said 900 people were killed in last week’s fighting in Goma between rebels and Congolese forces.