A rebel alliance claimed the capture of the biggest city in the Democratic Republic of Congo’s mineral-rich eastern region this week, pushing back against resistance from government troops backed by regional and UN intervention forces.

Thousands fled the city of Goma on Monday as fighting raged between Congolese forces and rebels backed by neighboring Rwanda, who claimed to have captured eastern Congo’s largest regional hub.

Goma is the capital of the conflict-battered North Kivu province, whose minerals are critical to much of the world’s technology. By capturing Goma, the rebels and their Rwandan allies would gain control of key border crossings, transport routes and a major airport – all of which are crucial to the lucrative mineral trade.