Democratic Republic of Congo President Felix Tshisekedi has vowed “a vigorous and coordinated response” against a rebel alliance that has besieged swaths of the nation’s mineral-rich east and forced hundreds of local troops and foreign mercenaries to surrender.

M23 rebels in the Democratic Republic of Congo were reported to have taken the key eastern city of Goma in fierce fighting with government forces that sent streams of refugees fleeing area communities.

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.