The UN human rights chief accused Rwanda-backed rebels who seized a second major city in eastern Democratic Republic of Congo (DRC) of killing children and attacking hospitals and warehouses storing humanitarian aid.

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.

M23 rebels backed by Rwanda took the city of Goma in a bloody battle. This weekend, the group entered the gold-trading center of Bukavu in eastern Congo after government soldiers fled.