Rwanda-backed rebels reached the center of east Congo’s second largest city, Bukavu, on Sunday morning and took control of the South Kivu province administrative office after little resistance from government forces, many of whom fled the rebels' advance.

Scores of residents cheering on the M23 rebels in central Bukavu on Sunday morning as they walked and drove around the city center after a dayslong march from the region's major city of Goma 63 miles (101 kilometers) away, which they captured late last month. Several parts of the city, however, remained deserted with residents indoors.

The M23 rebels are the most prominent of more than 100 armed groups vying for control of Congo’s mineral-rich east, and are supported by some 4,000 troops from neighboring Rwanda, according to the U.N.

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It was not clear if the rebels had taken decisive control of the city of about 1.3 million people. Their presence in central Bukavu is an unprecedented expansion of the rebels' reach in their yearslong fighting with Congolese forces. Unlike in 2012 when they only seized Goma in the fighting connected to ethnic tension, analysts have said the rebels this time are eyeing political power.

Many Congolese soldiers were seen on Saturday fleeing the rebels’ advance into Bukavu alongside thousands of civilians amid widespread looting and panic.

Congo’s President Felix Tshisekedi held a security meeting in the faraway capital of Kinshasa, where officials noted that Bukavu was “briefly” invaded by M23 but remains under the control of the Congolese army and allies from local militia, the presidency said on X. There were no signs of fighting or of Congolese forces in most parts of Bukavu on Sunday.

Tshisekedi has warned of the risk of a regional expansion of the conflict. Congo's forces are being supported in Bukavu by troops from Burundi and in Goma by troops from South Africa.

Burundi's president, Evariste Ndayishimiye, appeared to suggest his country will not retaliate in the fighting. In a post on X he said that “those people who were ready to get profit of the armed attack of Rwanda to Burundi will not see this.”

The Congo River Alliance, a coalition of rebel groups that includes M23, said it was committed to “defending the people of Bukavu” in a Saturday statement that did not acknowledge their presence in the city. “We call on the population to remain in control of their city and not give in to panic,” Lawrence Kanyuka, the alliance’s spokesperson, said in a statement.