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 conflict comes amid rising global tensions after Donald Trump’s election, especially between Washington and Beijing, over control of strategic minerals like those present in the Congo.

After a lightning offensive, M23 rebels now control Goma, a large city in the eastern Democratic Republic of Congo.