Rwanda-backed rebels claimed they captured eastern Congo’s largest city, Goma, early Monday, as the United Nations described a mass panic among its 2 million people and Congo’s government said the rebel advance was a “declaration of war.

Rwanda-backed rebels say they captured eastern Congo’s strategic city of Goma, the hub of a region containing trillions of dollars in mineral wealth that remains largely untapped.

The M23 militia, funded and directed by Rwanda, said it had seized the city of Goma, terrifying its people, many of whom sought shelter there after fleeing the rebel advance.