Crowds of Congolese police officers who switched to the M23 rebel group sang and clapped in occupied Bukavu city on Saturday, preparing for retraining under the authority of the Rwandan-backed rebels who are intent on showing they plan to stick around and govern.

M23 rebels in the Democratic Republic of Congo have captured the eastern city of Bukavu with the backing of Rwandan forces, the second major city in the mineral-rich Kivu region to fall in three weeks.

The U.N. Security Council unanimously adopted a resolution Friday demanding that the M23 rebels in eastern Congo immediately cease hostilities and withdraw from territories they have seized. The council also threatened sanctions on those who prolong the conflict.