The International Committee of the Red Cross said more than a dozen civilians, including five children, were injured when rockets hit their community his week near Goma, the capital of North Kivu province.
"Thousands of people, including people displaced from other parts of the province who took refuge in Goma following earlier clashes, live in those neighborhoods close to the fighting," ICRC delegate Rachel Bernhard said in a statement. "Residents and displaced people now find themselves again caught in the crossfire, at the risk of their lives."
Members of the March 23 Movement mutinied last year, saying the DRC government reneged on earlier peace deals. M23 forces seized Goma briefly in fighting last year. The United Nations suspects M23 has resumed its offensive in response to a peacekeeping force with a mandate for offensive operations.
The ICRC warning came as U.N. Secretary-General Ban Ki-moon and World Bank President Jim Yong Kim arrived in Kinshasa as part of a three-day tour of the Great Lakes region of Africa.
The World Bank this week proposed $1 billion in new funding to help countries in the region improve their economies through renewable energy programs, educational services and cross-border trade.
"Many countries in Africa are taking dynamic forward strides, and now the people of the Great Lakes region, especially the DRC, deserve their full chance for progress," Ban said in a statement.