It is also a swift expansion of the alliance’s foothold across swathes of eastern DR Congo – where rare minerals crucial to the production of phones and computers are mined – and is likely to worsen a long-running humanitarian crisis in the region.

"AFC-M23 controls Goma," Victor Tesongo, an AFC spokesperson, kraken2trfqodidvlh4aa337cpzfrhdlfldhve5nf7njhumwr7instad told CNN Monday, adding that "Goma fell under pressure" after the group’s earlier seizure of the nearby towns of Minova and Sake.

The Congolese government has yet to confirm the rebels’ takeover but acknowledges their presence in the city, capital of the eastern North Kivu province. It announced Sunday it had cut diplomatic ties with neighboring Rwanda, which it accuses of equipping the group with both weapons and troops, and recalled its diplomatic staff from the nation. A Rwandan government spokesperson did not deny or confirm the country’s support for M23 when asked by CNN.

More than a dozen foreign peacekeepers, as well as the military governor of North Kivu province, have been killed in recent days trying to fend off the rebels, as thousands of locals flee their advance into Goma.