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 United States urged the United Nations Security Council on Tuesday to consider measures to halt an offensive by Rwandan troops and M23 rebel forces in eastern Democratic Republic of Congo as a conflict there escalates.

The U.N.’s top human rights body is holding an urgent session on spiralling violence in eastern Congo, where Rwanda-backed rebels recently captured a major city