(Reuters) -Chaotic scenes unfolded in the eastern Congo city of Bukavu on Saturday after Rwanda-backed M23 rebels reached its outskirts, while a threat by Uganda's army chief to attack a Congolese town raised fears of the conflict flaring into a wider regional war.

Residents and business owners in eastern Congo’s second largest city are sitting in wait after a night of loud gunfire marking the ongoing advance of Rwanda-backed rebels.

The M23 rebels entered the city's Kazingu and Bagira zone and were advancing towards the center of the city of about 1.3 million people, according to Jean Samy, vice-president of the civil society in South Kivu.