Members of the March 23 Movement rebelled against the DRC government last year. The movement is suspected of committing war crimes during its siege on North Kivu province in the east of the country.
Violence in eastern DRC increased in recent weeks. The United Nations said it believes M23 is responding to the deployment of a special U.N. unit that is mandated to conduct offensive operations in the area.
Regional ICRC chief Franz Rauchenstein said the aid agency has received reports of "very violent attacks" on civilians in eastern DRC.
"Acts of violence committed against civilians, including murder and sexual assault, remain at a very worrying level and regularly cause the displacement of thousands of families," he said in a statement Friday.
Rauchenstein said the security situation in eastern DRC has taken a turn for the worse. The fate of thousands of civilians trapped by conflict in the region "hangs in the balance," he said.
M23 rebel leader Bosco Ntaganda turned himself into the International Criminal Court this year to face war crimes charges. Suspected M23 crimes include the use of rape as a weapon of war and conscription of child soldiers.