“The secretary-general will be writing to the government of Nigeria to express his condolences,” Stephane Dujarric, the spokesperson, said at a regular news conference.

On Wednesday, at least 12 pupils have been confirmed dead following the collapse of the three-storey building which housed a primary school in Lagos in southwestern Nigeria, according to a hospital source.

Governor of Lagos State Akinwunmi Ambode said a thorough investigation would be launched into the incident.

The building, located in Ita-Faji area of Lagos, had collapsed, leaving several dead and others injured on Wednesday.