Crowd cheers M23 rebels advancing south in eastern DRC

Armed men wearing military fatigues have been seen in the towns of Katana and Kabamba as the Rwandan-backed rebel group M23 advanced toward the South Kivu provincial capital, Bukavu. In Kavumu, where Bukavu airport is located, gunfire was heard as armed men advanced through the street. Authorities reportedly fled Bukavu as the rebels advanced south
Rwandan-backed M23 rebels seize key DRC airport in rapid southern advance
Who are the M23 rebels and why is there fighting in eastern DRC?