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.

Burundi is withdrawing its forces from eastern Democratic Republic of Congo where they had been fighting against M23 rebels, four sources said on Tuesday, in a further blow to Congo's army as it struggles to halt a rebel advance.

Nearly three thousand people have been killed in the city of Goma in the eastern Democratic Republic of Congo, according to the United Nations, after the provincial capital was captured by rebels following days of fierce fighting with the Congolese army.