Crowds fled as gunfire rang out at a rally held by the leader of the M23 rebel group, Corneille Nangaa, in Democratic Republic of Congo's eastern city of Bukavu on Thursday, residents said.

There was no immediate information on who was shooting, or whether there were any deaths or injuries at the event organised by the force that has battled Congo's army and seized swathes of territory in the east since the beginning of the year.

Congo, the United Nations and Western powers say neighbouring Rwanda is backing the M23 group - accusations Rwanda denies. The rebel advance has stirred fears of a regional war that could draw in Congo's neighbours.

It was Nangaa's first public appearance in eastern Congo's second largest city since his forces seized control of it nearly two weeks ago.

M23 has been trying to demonstrate that it can restore order in the territory it has captured from Congo's army, and has re-opened ports and schools.

This M23 advance is the gravest escalation in more than a decade of the long-running conflict in eastern Congo, rooted in the spillover of Rwanda's 1994 genocide into Congo and the struggle for control of Congo's vast minerals resources.

Rwanda has said it is defending itself against the threat from a Hutu militia, which it says is fighting with the Congolese military.