Rwanda's ally Uganda, unhappy about another rebel group in DR Congo that threatens its security, has also been accused of helping the M23 - with its officers also spotted at Tchanzu. The UN experts say Uganda has also supplied weapons, hosted rebel leaders and allowed cross-border movements of M23 fighters - accusations Kampala denies.

Rwanda's President Paul Kagame said he agreed with the U.S. government on the need for a ceasefire in eastern Congo but gave no indication of bowing to calls for Rwandan troops and the M23 rebels they support to withdraw from Goma.

Rwandan-backed M23 rebels asserted their control over east Congo's largest city Goma on Thursday by calling on residents to resume normal life, even as the group clashed with Congolese troops as they tried to take more territory.