REBEL forces have entered the last government-held city in mineral-rich eastern Democratic Republic of Congo, in an offensive that has forced thousands to flee across the border into Burundi, residents say.
Heavy artillery and gunfire could be heard in Uvira, with terrified residents describing the situation as chaotic.
The escalation in fighting comes despite the peace deal brokered by US President Donald Trump last week between DR Congo’s President Félix Tshisekedi and Rwanda’s Paul Kagame to end the long-running conflict.
The M23 rebel group said it had “liberated” the city, while UN-backed Radio Okapi quoted residents as saying that rebel fighters were on major streets.
However, South Kivu Governor Jean-Jacques Purusi told local media that the army and allied militia remained in control of the city, which is just 27km (17 miles) from Burundi’s capital, Bujumbura, across Lake Tanganyika.
Burundi has shut its border with DR Congo, a Burundian military source was quoted as saying by AFP news agency.
One resident told the BBC that armed M23 fighters had marched in a single column into Uvira from the north-east on Wednesday, meeting no resistance.
Some residents cheered their arrival, the resident said.
The city was in lockdown, with shops and schools closed as most people stayed indoors.
“Three bombs have just exploded in the hills. It’s every man for himself,” one resident told AFP, while another added: “We are all under the beds in Uvira – that’s the reality.”
A local rights official told AP news agency that there was a “risk of a massacre” if the remaining soldiers mounted strong resistance.
“It’s chaotic, nobody’s in charge. Uvira is done for,” a Burundian officer told AFP.
Military and security sources said the rebel fighters advanced from the north, near the Burundian border.
Burundi has several thousand troops in eastern DR Congo in support of the government. Its leader Évariste Ndayishimiye flew to Washington last week to observe the signing of the peace accord that Trump hailed as a “miracle”.
Burundi’s Foreign Minister Edouard Bizimana called the M23 advances “a slap in the face… a middle finger” to Washington’s efforts in brokering a peace agreement.
“Signing an agreement and not implementing it is a humiliation for everyone, and first and foremost for President Trump,” he told AFP, adding that they have seen “several trucks full of soldiers” coming as reinforcements from Rwanda.
On Tuesday, the US, European Union, and eight European nations accused Rwanda of supporting the rebel offensive, and called for an immediate halt to the fighting
In a joint statement, they voiced “profound concern” about the violence, and said it had a “destabilising potential for the whole region”.
They urged the Rwanda Defence Force (RDF) to “immediately halt offensive operations” in eastern DR Congo, and called on its troops to withdraw from the region.
A spokesman for the US state department said that Rwanda “continues to provide support to M23 [and] must prevent further escalation”.
But Rwanda has denied any involvement in the fighting, accusing DR Congo’s government and Burundi of violating the ceasefire.
In a statement on X, the Rwandan foreign ministry said the ceasefire violation “cannot be placed on Rwanda” and said the Congolese and Burundian armies had “systematically” bombed villages close to Rwanda’s border.