At least 42 school-age children and a teacher were killed in a Saturday terrorist attack on a boarding school in Mamudo in northeastern Nigeria. Islamic radical group Boko Haram was suspected of carrying out the attack.
OIC Secretary-General Ekmeleddin Ihsanoglu expressed grave concern during the weekend violence, calling on the Nigerian government to ensure justice is brought to those responsible.
The Nigerian government in June declared a state of emergency in the northern states in response to violence attributed to Boko Haram.
Ihsanoglu said the Islamic organization's principles "vigorously" oppose acts of terrorism or violent extremism. Nigeria is a member of the OIC, an organization tasked with upholding Islamic doctrines.
Muslims across the world are marking the holy month of Ramadan, a period of ceremonial fasting. Nigerian authorities said last week they were easing security restrictions to give Muslims the opportunity to observe their religious obligations.
Catherine Ashton, the foreign policy chief for the European Union, called the attack on the school "horrific."