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.

"It was a terrible night," local sources told Fides from Goma, the capital of North Kivu, in the east of the Democratic Republic of Congo, which was conquered today, January 27, by the rebels of the M23 movement.

Gunfire rang out early on Monday across parts of Goma, the largest city in eastern Congo, hours after Rwanda-backed rebels said they had seized the city despite the United Nations Security Council's calling for an end to the offensive.

The AFC/M23 rebels early Monday, January 27, announced that they captured Goma, the capital of eastern DR Congo's North Kivu Province. The rebels announced the city's capture in a statement minutes before a 48-hour deadline imposed by the group for the Congolese army to surrender their weapons expired.

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

Congolese rebels said on Sunday they had taken Goma, the biggest city in the east of the mineral-rich country, after a lightning advance that has forced thousands of people to flee and fueled concerns of a regional war.

A U.N. official says Congolese rebels and allied Rwandan forces have entered the outskirts of Goma and the airport in the key eastern city is no longer in use.

The Democratic Republic of Congo withdrew its diplomats from Kigali as the Rwanda-backed M23 fighters advanced on the key city of Goma in the east of the country.

Jambojet has suspended Nairobi-Goma flights after M23 rebels announced the seizure of a key eastern Democratic Republic of Congo (DRC) city.

Corneille Nangaa orchestrated the heavily criticised vote that handed President Felix Tshisekedi power. Today, he is the public face of a sprawling coalition of Congolese politicians and rebel groups fighting to oust him.

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