Residents in eastern Congo’s largest city of Goma are fleeing after Rwanda-backed rebels claimed to have captured the regional hub from Congolese forces.

Video showed inmates escaping a prison in the Democratic Republic of Congo as Rwandan-backed M23 rebels entered the eastern city of Goma. Thousands of civilians and Congolese soldiers fled to neighboring Rwanda in the latest escalation of conflict in the region.

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.

Rwandan-backed M23 rebels marched into the centre of Goma, the largest city in the eastern Democratic Republic of Congo.

Back in 2012, pressure on Paul Kagame, Rwanda’s president, by donor countries including America preceded a swift ouster from Goma of M23 by UN peacekeepers. That scenario seems less likely this time around.

Residents of Goma reported gunfire and shelling after rebels overran Congolese troops. U.N. officials estimated that more than one million displaced people were now inside the city.

Kenyan President William Ruto said Monday that the presidents of Rwanda and Congo have agreed to attend a meeting Wednesday to discuss developments in eastern Congo, where M23 rebels say they have seized control of Goma on the Congo-Rwandan border.

Heavy artillery fire could be heard in Goma on Monday, hours after Rwandan troops and fighters from the M23 rebel group entered the capital of North Kivu Province. The UN has warned of a looming crisis.

Congo has severed diplomatic ties with Rwanda as fighting between Rwanda-backed rebels and government forces rages around the key eastern city of Goma.

The besieged Congolese city of Goma was rocked by heavy artillery fire on Monday as France warned the regional capital was on the brink of falling to militia fighters and

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.