Rwanda-backed rebels appeared to be heading toward a third major city in eastern Congo, frightened residents said Tuesday, as international pressure rose over the M23's expansion in the mineral-rich region that's critical for global technology.

The UN's human rights chief accuses Rwanda-backed M23 rebels of killing children and attacking hospitals in eastern Congo. M23, having seized cities Bukavu and Goma, is accused of seeking control over Congo's mineral-rich region with Rwanda's support.

M23 rebels in the Democratic Republic of Congo have captured the eastern city of Bukavu with the backing of Rwandan forces, the second major city in the mineral-rich Kivu region to fall in three weeks.