Rwanda-backed rebels claimed on Monday they captured eastern Congo’s strategic city of Goma, the hub of a region containing trillions of dollars in mineral wealth that remains largely untapped.

Democratic Republic of Congo President Felix Tshisekedi, speaking publicly for the first time since Rwandan-backed rebels seized the eastern city of Goma, said his government was preparing a response and warned of “unpredictable consequences” for the region.

Rebels appear to be edging closer to taking control of the key city of Goma in the east of the Democratic Republic of Congo following reports that they had captured its airport. The Congolese government has insisted that it is still in charge as fighting in parts of the city continues.