Over 1,000 Burundian troops have been covertly deployed in eastern Democratic Republic of Congo since October, wearing the uniform of Congolese troops and working alongside them in the fight against M23 rebels, an unpublished U.N. report seen by Reuters showed. Citing security and intelligence sources and sources close to Congolese army command, the report by the U.N. Group of Experts in Congo said the troops were airlifted from Burundi to eastern Congo by Congolese army planes starting from Sept. 21.