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.

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

Rwanda has been urged to withdraw its advancing troops from the outskirts of Goma, a mineral-rich city in the Democratic Republic of Congo (DRC).