The rebels, which Rwanda denies supporting, have long been funded at least in part by the illicit mineral trade.

Rebels seized the airport of east Congo's largest city, Goma, on Tuesday, potentially cutting off the main route for aid to reach hundreds of thousands of displaced people, after capturing the city in an offensive that left dead bodies lying in the streets.

There was gunfire Tuesday in the eastern Democratic Republic of Congo city of Goma, as the United Nations warned of a worrying humanitarian situation amid clashes between Congolese soldiers and Rwandan-backed rebels who attacked the area and claimed to be in control.