BUKAVU, Congo — Rwanda-backed rebels have “occupied” a second major city in mineral-rich eastern Congo, Congo’s government said Sunday, as M23 rebels positioned themselves at the governor’s office in Bukavu and pledged to clean up after the “old regime.”

Associated Press journalists witnessed scores of residents cheering on the rebels after they entered Bukavu following a dayslong march from Goma, a city of 2 million people they seized last month.

The rebels saw little resistance from government forces against the unprecedented expansion of their reach after their years of fighting. The government vowed to restore order in Bukavu, a city of 1.3 million people, but there was no sign of soldiers. Many were seen fleeing Saturday alongside thousands of civilians.

M23 rebels are the most prominent of more than 100 armed groups vying for control of eastern Congo’s trillions of dollars in mineral wealth that’s critical for much of the world’s technology. The rebels are supported by about 4,000 troops from neighboring Rwanda, according to United Nations experts.

The fighting has displaced more than 6 million people in the region, creating the world’s largest humanitarian crisis.

Bernard Maheshe Byamungu, one of the M23 leaders who has been sanctioned by the U.N. Security Council for rights abuses, stood in front of the South Kivu governor’s office in Bukavu and told residents they have been living in a “jungle.”

“We are going to clean up the disorder left over from the old regime,” he said, as some in the small crowd of young men cheered the rebels on to “go all the way to Kinshasa,” Congo’s capital, nearly 1,000 miles away.

M23 did not announce any seizure of Bukavu, unlike its announcement when taking Goma, which brought swift international condemnation.

On social media, Congo’s communications ministry acknowledged for the first time that Bukavu had been occupied and said the national government was “doing everything possible to restore order and territorial integrity” in the region.

Bukavu resident Blaise Byamungu said the rebels marched into the city that had been “abandoned by all the authorities and without any loyalist force. Is the government waiting for them to take over other towns to take action? It’s cowardice.”

Unlike in 2012, when M23 briefly seized Goma and withdrew after international pressure, analysts have said the rebels this time are eyeing political power.

The fighting in Congo has connections with an ethnic conflict that’s decades long. M23 says it is defending ethnic Tutsis in Congo. Rwanda claims that Tutsis are being persecuted by Hutus and former militias responsible for the 1994 genocide of 800,000 Tutsis and others in Rwanda. Many Hutus fled to Congo after the genocide and founded the Democratic Forces for the Liberation of Rwanda militia group.

Rwanda says the militia group is “fully integrated” into the Congolese military, which denies it.