Taking advantage of its turn as president of the Security Council, Moscow sent Foreign Minister Sergey V. Lavrov to preside over a session on peace and diplomacy.

A prosecutor opened an investigation into the killing of about 60 people by men in uniforms of the national military. Days earlier, the authorities said they would investigate the killing of seven boys.

Many of the victims are believed to have been members of a church led by a pastor who is being investigated on allegations that he directed his congregants to starve themselves to death.

The clashes have killed more than 400 people and injured thousands more. Those displaced are streaming into nations such as Chad, Egypt and South Sudan, adding to a refugee crisis in the region.