GOMA, Democratic Republic of Congo (Reuters) -Rwandan-backed rebels marched into east Congo's largest city Goma on Monday and troops from the east African neighbours exchanged fire over the border in the worst escalation of the long-running conflict for more than a decade.

After 3 UN peacekeepers were killed in eastern Congo, Guterres emphasised that attacks against UN staff may constitute a war crime United Nations chief Antonio Guterres called on Sunday on Rwandan forces to withdraw from Democratic Republic of Congo (DRC) and halt support for fighters advancing on the key Congolese city of Goma.

M23 rebels, reportedly backed by Rwanda, claimed control of Goma, the largest city in eastern Congo, early Monday. This development comes as the Congolese government cut diplomatic ties with Rwanda, with Congolese spokesman Patrick Muyaya calling the situation a "declaration of war.

Gunshots rang out Sunday night in the centre of the besieged Congolese city of Goma, AFP journalists heard, after the Democratic Republic of Congo accused Rwanda of sending fresh troops across the border to capture the strategic hub.

United Nations chief Antonio Guterres on Sunday urged Rwanda to withdraw its forces from the eastern Democratic Republic of Congo where fierce fighting raged as Kigali-backed fighters closed in on the major city of Goma.

The UN chief Antonio Guterres said Rwanda was backing M23 rebels as they advance towards the city of Goma in the Democratic Republic of Congo. DW has more.

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

United Nations chief Antonio Guterres has called on Rwandan forces to withdraw from the Democratic Republic of the Congo (DRC) and halt support for M23 fighters advancing on the key city of Goma ...

Gunfire broke out on Sunday night in the centre of the besieged Congolese city Goma after the Democratic Republic of Congo accused neighbouring Rwanda of sending more troops across the border to help pro-Kigali fighters capture the provincial capital.

A conflict that has raged for decades reached a flashpoint this week when rebels backed by Rwanda marched on a key Congolese city in a bid to occupy territory and exploit minerals.

U.S. Secretary of State Marco Rubio told Rwandan President Paul Kagame on Tuesday that Washington was "deeply troubled" by escalation in the conflict in the Democratic Republic of Congo, particularly the fall of the city of Goma to Rwandan-backed rebels.