Twelve people have died and more than 100 were believed to be trapped after a building caved in on Wednesday morning in Lagos, Nigeria's commercial capital, with an unknown number feared missing in the chaos.

At least 25 children were rescued from the rubble of the three-storey structure on Wednesday, which had a private school on the third floor. Forty three people were injured and taken to hospital.

Locals and emergency services took part in a desperate combined rescue operation, with some people digging with their bare hands through dusty concrete slabs and exposed metal to find people trapped underneath.

Many people were brought out motionless but full casualty figures were unknown as of Wednesday evening, a witness told The Daily Telegraph.

Footage circulating on social media showed crowds of people overlooking the scene, cheering on the rescue team as they continued the frantic search.