GOMA, Democratic Republic of Congo (Reuters) -Congolese M23 rebels entered the centre of the eastern city of Goma on Monday, two witnesses said, hours after they claimed to have seized the city despite the United Nations Security Council demanding an end to the offensive.

M23 rebels claim they now control the Congolese city of Goma—an act Congo's government described as a 'declaration of war.'

The latest fighting has intensified a humanitarian crisis, displacing more than 400,000 people since the start of the year, and raised fears of sparking a regional war, the U.N. has warned.