Bombs and bullets continued to fly across the common border on Monday following the capture of Goma city in eastern Congo by M23.

Suspects were found in possession of $400,000 in cash and substantial amount of gold, raising concerns about scale of their operations and potential involvement of organized networks

A Chinese envoy on Sunday strongly condemned the March 23 Movement (M23) rebels in the Democratic Republic of the Congo (DRC) for attacking local people and the UN peacekeepers, demanding that it immediately stop the offensive.

Heavy artillery fire could be heard in Goma on Monday, hours after Rwandan troops and fighters from the M23 rebel group entered the capital of North Kivu Province. The UN has warned of a looming crisis.

The M23 rebel group, which has taken control of large parts of the eastern Democratic Republic of Congo (DRC) in recent years, now says it has captured the key city of Goma, the largest in the area, from government forces.

Many Congolese see the rebel advance as an invasion of their country by a foreign power in an attempt to seize land and Congo’s valuable rare minerals.

M23 rebels in the Democratic Republic of Congo were reported to have taken the key eastern city of Goma in fierce fighting with government forces that sent streams of refugees fleeing area communities.

M23 rebels marched into east Congo's largest city Goma on Monday and Congolese troops exchanged fire with the Rwandan military across the border, in the worst escalation of a long-running conflict for more than a decade.

Fighting across the largest city in eastern Democratic Republic of Congo and "is still very much ongoing ... it's not over yet," senior U.N. official in Congo, Bruno Lemarquis, said on Monday after Rwandan-backed M23 rebels claimed to have control of Goma.

An insurgency led by M23 rebels in eastern Congo has escalated and reached the city of Goma, worsening a humanitarian crisis in a region that suffered two devastating wars between 1996 and 2003.

The M23 militia, funded and directed by Rwanda, said it had seized the city of Goma, terrifying its people, many of whom sought shelter there after fleeing the rebel advance.