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.

As Rwanda-backed rebels strolled through the streets of eastern Democratic Republic of Congo's second-largest city, President Felix Tshisekedi's office claimed it was actually still controlled by his army and "valiant" allied forces.