(Reuters) -Chaotic scenes unfolded in the eastern Congo city of Bukavu on Saturday after M23 rebels reached its outskirts, while Congo's prime minister declined to comment on a threat by Uganda's army chief that raised fears of a spiral into a wider regional war.

"The fighting that is raging in South Kivu — as a result of the continuation of the M23 offensive — threatens to push the entire region over the precipice," Guterres said without mentioning Rwanda. "And the sovereignty and territorial integrity of the DRC must be respected," Guterres added.

Analysts say the deadly march by Rwanda-backed rebels across eastern Congo could widen into a regional conflict drawing in even more countries, and two neighboring nations with the most involvement in the mineral-rich area might be the key to stopping the violence.