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, said it took the city of Goma, terrifying its people, many of whom sought shelter there after fleeing the rebel advance.

Gunfire rang out across parts of Goma, the largest city in the eastern Democratic Republic of the Congo (DRC), hours after Rwanda-backed M23 rebels said they had seized it despite the United Nations Security Council calling for an end to the offensive.