Katanty and Sonia Rolley GOMA, Democratic Republic of Congo (Reuters) -Rwandan-backed rebels marched into east Congo's largest city Goma on Monday and Congolese troops exchanged fire with the Rwandan military across the border,

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

Fighting between M23 and Democratic Republic of the Congo forces has displaced 400,000 since the start of this year, according to the United Nations

Residents of eastern Congo's largest city of Goma greeted the arrival of Rwanda-backed rebels with trepidation on Monday, some staying indoors and others coming out to cheer in what one called a "show" of happiness.

Congo has severed diplomatic ties with Rwanda as fighting between Rwanda-backed rebels and government forces rages around the key eastern city of Goma, leaving at least 13 peacekeepers and foreign soldiers dead and displacing thousands of civilians.

Mount Goma

M23 rebels said they have advanced into Goma, a large city in the eastern Democratic Republic of Congo. Hundreds of thousands of residents have been displaced.

In the aftermath of its withdrawal from Goma, the M23 suffered a series of heavy defeats at the hands of the Congolese army, which was backed by a multinational force. The M23 were subsequently expelled from the country. M23 fighters then agreed to be re-integrated into the army in return for promises that Tutsis would be protected.

PARIS (Reuters) - 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, two United Nations sources said on Monday.

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

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