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.

President of the Democratic Republic of Congo said on Thursday that his troopers are fighting an insurgence by the Rwandan-backed militant group M23 which recently captured swaths of land in the east.

Unconfirmed reports say the Rwanda-backed rebels are currently advancing towards Bukavu, the second-biggest city in the mineral-rich east, despite international calls for a ceasefire. In a televised address after the fall of Goma,