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.

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.

The rebel group M23 declared a ceasefire in areas under its control in the eastern Democratic Republic of the Congo, citing humanitarian reasons. The streets of Goma were busy as aid groups rushed Tuesday to help the thousands of people wounded and displaced during the past week’s fighting between M23 and pro-Congolese government forces.