"The universal right to education is still contested in some places, and I take this opportunity to condemn the abduction of more than 270 girls in Nigeria by extremist groups," Unesco director-general Irina Bokova said in a statement.
"This is an unacceptable violation of human rights. It is an attack against the aspirations of these girls. It is an attack against the future of Nigeria. No belief can justify this act," she added.
Speaking at the "Global Education for All Meeting" in Muscat, Bokova said: "Our response to such extremism is clear."
"We must never relent in providing every girl and boy with a quality education. We must never tire in supporting education as a force for human dignity and sustainable development. This calls for greater cooperation and coordination among States. We(Unesco) are determined to support the Nigerian government to 'bring back our girls'," she added.
Members of the militant group Boko Haram abducted more than 200 girls from the Government Secondary boarding school in the town of Chibok, several hundred km east of Abuja, on the night of April 14. The incident has drawn international condemnation.