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.

The M23 armed group and Rwandan soldiers entered the centre of Goma on Sunday night after weeks of advancing on the main city in the Democratic Republic of Congo's North Kivu province.

The Congolese government, alongside U.N. officials and Western powers, including the United States, has accused neighbouring Rwanda of exacerbating the conflict by deploying thousands of troops and heavy weaponry in support of M23.