Nearly 3,000 people have been killed in the city of Goma in the eastern Democratic Republic of Congo, according to the United Nations, after it was captured by rebels following days of fierce fighting with the Congolese army.

Officials and residents say Rwanda-backed rebels have gained ground in eastern Congo despite the unilateral ceasefire they declared earlier this week, taking control of a town 100 kilometers (60 miles) from the provincial capital of Bukavu.

Rwandan-backed M23 rebels captured the mining town of Nyabibwe in eastern Congo’s South Kivu province, violating a ceasefire they declared earlier this week, according to NBC News. The rebels now advance toward Bukavu, raising fears of further conflict after seizing the city of Goma last week.

When M23 rebels swept into the Congolese city of Goma this week, world powers urged them to immediately withdraw. Instead, the Rwanda-backed insurgents are intent on showing they can restore order and govern.

The Rwanda-backed rebels who captured a major city in eastern Congo have sought to reassure its residents about their safety