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

Troops from Democratic Republic of Congo and Rwanda have been firing at each other across their shared border in the eastern Congolese city of Goma, where Rwandan-backed rebels launched an offensive,

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.

Hundreds of people attempted to flee the Democratic Republic of Congo to Rwanda on Sunday, as heavy gunfire resonated across the key eastern Congolese city of Goma, just a few miles from the frontline.

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.

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.

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.

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.

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