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.'

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.

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,

Mount Goma

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

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.

The M23 armed rebel group said it has captured the Democratic Republic of the Congo’s eastern city of Goma on Monday.

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.

M23 vows to defend Tutsi interests, particularly against ethnic Hutu militias such as the FDLR, which was founded by Hutus who fled Rwanda after participating in the 1994 genocide