A de facto ceasefire between Congolese forces and Rwandan-backed rebels in the eastern Congo town of Walikale appeared to have broken down on Monday, with the rebels going back on a pledge to withdraw and accusing the army of violating its own commitments.

Rwanda-backed rebels battling Congo’s army have pushed into a strategic, mineral-rich town in the east, ignoring calls for a ceasefire this week by the Congolese and Rwandan presidents as the M23 rebel group expands its footprint in the conflict-torn African country.

The leader of the rebels who captured two key cities in eastern Congo says international sanctions and the planned minerals deal that the country has offered the U.S. will not stop the fighting in the conflict-hit east.