A rebel group in Congo that overran and briefly held a regional capital in the country's east is accusing the government of refusing to negotiate.

The M23 rebels only agreed to retreat from the city of Goma last year after the government agreed to talks.

In a letter to the U.N. Secretary-General's special envoy for the Great Lakes region, M23 president Bertrand Bisimwa wrote that the government delegates have told mediators they will no longer negotiate with M23.

The letter also accuses the Congolese army of preparing an imminent attack on the M23.

Last month M23 fighters and the Congolese military exchanged fire for days in fighting.