A three-story building housing a school collapsed Wednesday morning in Lagos, Nigeria's commercial capital, officials and eyewitnesses said.

Many students and residents are feared trapped in the building which collapsed at around 9.30 am Wednesday in the Itafaji area of Lagos Island, a Red Cross official said.

Six children were pulled out of the rubble by rescue workers at the scene, Nigerian Red Cross official Raheem Jamiu said.

The rescued students are now receiving medical attention.

The number of deaths is still unconfirmed, but rescue efforts are on-going at the mixed-use building.

Anxious parents waiting for their children to be rescued in the building said many buildings in the commercial hub in downtown Lagos are not safe.

"A lot the buildings here are not safe even from looking at the building, you should know no school should be here," Wale Wasiu said.

Building collapses are frequent in Nigeria.

At least 100 worshippers were killed in a church in the southern state of Akwa Ibom after the roof caved in during a Sunday service in 2016.

In 2014, more than 70 people died after a two story guest house in a church collapsed in Lagos.