Congo's government on Tuesday described the unilateral ceasefire declared by Rwanda-backed rebels in eastern Congo as “false communication,” while the United Nations noted reports of heavy fighting with Congolese forces in the region.

The Eastern Congo rebel alliance that includes the M23 has declared a ceasefire for humanitarian reasons starting on Feb. 4, the group known as the Congo River Alliance said in a statement.

Rwandan-backed M23 rebels captured the mining town of Nyabibwe in eastern Congo’s South Kivu province, violating a ceasefire they declared earlier this week, according to NBC News. The rebels now advance toward Bukavu, raising fears of further conflict after seizing the city of Goma last week.