Forces of the Democratic Republic of Congo were losing control of the key city of Goma on Wednesday after rebel groups backed by Rwanda took over the airport and shared plans to set up a new administration.

Democratic Republic of Congo's M23 rebels are moving south towards Bukavu, the capital of South Kivu province, in what appears to be an attempt to expand their area of control in the country's east after capturing the city of Goma.

A rebel alliance claimed the capture of the biggest city in the Democratic Republic of Congo’s mineral-rich eastern region this week, pushing back against resistance from government troops backed by regional and UN intervention forces.

The Democratic Republic of Congo’s government says the Rwanda-backed rebels’ advance constitutes a “declaration of war."

By Yassin Kombi and Sonia Rolley GOMA, Democratic Republic of Congo (Reuters) -The United States told Rwanda it was "deeply troubled" by the fall of Goma in eastern Congo to Rwandan-backed M23 rebels,

Goma residents warily venture outside after M23 rebels take control of the city"We are in Congo, but already, we are under the control of the M23 rebels. And now, it feels like we are in a dual nation.

United Nations officials say there were dead bodies on the streets of eastern Congo’s largest city where hospitals are overwhelmed and hundreds of thousands are fleeing gunfire and shelling.

The United Nations says troops from the M23 rebel group, as well as their Rwandan allies, have entered Goma in the Democratic Republic of Congo. In recent weeks, the rebels have captured several key towns.

Rwanda-backed rebels captured large parts of Goma, the biggest city in eastern Congo, including its airport, the United Nations said, as Rwanda's president on Wednesday joined calls for a ceasefire in the decadeslong conflict amid mounting international pressure.