Rebels seized the airport of east Congo’s largest city Goma on Tuesday, potentially cutting off the main route for aid to reach hundreds of thousands of displaced people, after capturing the city in an offensive that left dead bodies lying in the streets.

Rebels led by the M23 group claim to have taken control of Goma, a key city in the eastern Democratic Republic of the Congo.

Residents of eastern Congo's largest city of Goma greeted the arrival of Rwanda-backed rebels with trepidation on Monday, some staying indoors and others coming out to cheer in what one called a "show" of happiness.

Congo has severed diplomatic ties with Rwanda as fighting between Rwanda-backed rebels and government forces rages around the key eastern city of Goma.

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.

Democratic Republic of Congo's M23 rebel group has gained control of the airport in the eastern city of Goma, diplomatic and security sources told Reuters.

Rwanda-backed M23 rebels faced pockets of resistance from army and pro-government militia overnight after entering eastern Congo's largest city Goma in the worst escalation of a conflict that has run for more than a decade.

The UN and global powers fear the conflict could spiral into a regional war akin to those of 1996-1997 and 1998-2003 that killed millions.

A lightning advance in Congo's mineral-rich eastern borderlands is set to boost the M23 rebellion's illegal mining revenues, with analysts predicting a further surge in illicit trade in minerals including coltan and gold through neighbouring Rwanda.

The M23 rebels are one of about 100 armed groups vying for a foothold in the mineral-rich region in the conflict, one of Africa’s largest.