Rwanda-backed rebels claimed they captured eastern Congo’s largest city of Goma early on Monday, as the United Nations described a mass panic among its two million people and Congo’s government said the rebel advance was a “declaration of war."

The M23 rebels announced the city's capture in a statement minutes before a 48-hour deadline expired that had been imposed by the group for the Congolese army to surrender their weapons.

Early on Monday morning, gunfire was heard throughout the city, according to two aid workers sheltering there who were not authorised to speak to the media.

In a statement, the rebels urged residents of Goma to remain calm and for members of the Congolese military to assemble at the central stadium.

The M23 rebels’ offensive in the heart of the mineral-rich region threatens to dramatically worsen one of Africa’s longest wars and further displace civilians.

According to a United Nations report, over a third of the population of North Kivu province where Goma is located are currently displaced and the capture of Goma will likely exacerbate the situation.

Late Sunday night, UN peacekeepers began to process members of the military who had begun to surrender on the outskirts of the city.

Congolese government spokesman Patrick Muyaya made a statement in a video posted on X calling for the protection of civilians and saying the country is “in a war situation where the news is changing.”

French Foreign Minister Jean-Noel Barrot said the Rwanda-backed offensive "must stop", expressing his country's solidarity with the Democratic Republic of Congo.

With international pressure mounting for an end to the battle for Goma, Kenya announced on Sunday that Congolese President Felix Tshisekedi and Rwandan President Paul Kagame had agreed to attend a summit in the next two days.

M23 fighters and 3,000 to 4,000 Rwandan soldiers had been laying siege to Goma for several days, according to the United Nations and security sources. (Agencies)