The Rwanda-backed rebels who captured a major city in eastern Congo have sought to reassure its residents about their safety.

Nearly three thousand people have been killed in the city of Goma in the eastern Democratic Republic of Congo, according to the United Nations, after the provincial capital was captured by rebels following days of fierce fighting with the Congolese army.

Rwandan-backed M23 rebels in Democratic Republic of Congo are seeking to advance south towards Bukavu, the capital of South Kivu province, in an attempt to expand their area of control in the country's east after capturing the city of Goma.

Rebels occupying the eastern Democratic Republic of Congo city of Goma have declared a cease-fire but the government dismissed the pause in the fighting as a ruse aimed to head off growing international concern.

Bodies are decomposing on the streets of Goma that have not yet been collected, with hundreds of thousands displaced in the region after fighting between Rwanda-backed rebels and Congolese forces.

France expresses its solidarity regarding the Democratic Republic of Congo and condemns actions by Rwanda in the country, French Foreign Minister Jean-Noel Barrot said on Monday.

A rebel group that claimed to have captured the city of Goma in the eastern Democratic Republic of Congo last week has called for an immediate humanitarian ceasefire, after fighting with the Congolese military has left hundreds of people dead.