Nigerian authorities said at least 23 people were killed this month when gunmen attacked six villages in the African nation's Plateau state.
The attacks were believed to be the work of Fulani mercenaries, ethnic Muslim herdsmen who have been at odds with Christian villagers in the region.
The ICRC said more than 5,500 people were displaced by the conflict in the central Nigerian state. Julia Unger, a regional ICRC delegate, said most people were forced to flee their homes with just the clothes on their back.
"They have urgent needs in terms of food, water and basic household items," she said in a statement.
The ICRC described the security situation in the region as "unpredictable."
Religious violence has troubled Nigeria, a country divided along Muslim and Christian lines. Boko Haram, a militant group in the country, is allegedly seeking an Islamic state.
Nigerian President Goodluck Jonathan, a Christian, said his country would work with the International Criminal Court on investigating Boko Haram.