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

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.

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.

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.

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.