The UN chief made the remarks in the three-month report on the MONUSCO peacekeepers in Congo, published on Tuesday.
MONUSCO is the French acronym for United Nations Organization Stabilization Mission in the Democratic Republic of the Congo.
“MONUSCO’s observations of the command and control ability of the attacking force, the effective coordination of its fire support, the quality of its equipment and its general fighting ability, particularly during night time, all suggested the existence of external support, direct and indirect,” Ban said. “The subsequent speed, efficiency and success of the M23’s renewed offensive were rendered possible by a sudden increase in the group’s combatants, coordinated multi-pronged attacks, and attacks with coordination between infantry and fire support,” Ban added.
The M23 rebels seized the eastern city of Goma on November 20, 2012 after UN peacekeepers gave up the battle for the frontier city, which is home to about one million people. The rebels withdrew from the city on December 1 under a ceasefire accord.
The UN has previously accused neighboring Rwanda and Uganda of helping rebels in the eastern Congo, an accusation both countries vehemently deny.
The M23 rebels defected from the Congolese army in April 2012 in protest over alleged mistreatment in the Armed Forces of the Democratic Republic of Congo (FARDC). They had previously been integrated into the Congolese army under a peace deal signed in 2009.
Since early May 2012, nearly 3 million people have fled their homes in the eastern Congo. About 2.4 million have resettled in Congo, but more than 460,000 have crossed into neighboring Rwanda and Uganda.Congo has faced numerous problems over the past few decades, such as grinding poverty, crumbling infrastructure, and a war in the east of the country that has dragged on since 1998 and left over 5.5 million people dead.