Lagos, Nigeria: Rescue workers in Nigeria hunted for survivors Sunday inside an evangelical church where the roof caved in on worshippers a day earlier, killing at least 60.

Emergency services in the remote southeastern city of Uyo, the capital of Akwa Ibom state, raised the toll to 60 "confirmed" dead.

Hospital sources said 200 others had been treated for injuries. 

The Reigners Bible Ministry was packed on late Saturday morning when the roof -- which was still under construction -- collapsed on the congregation.

The state-run Nigerian News Agency said "between 50 and 200" people could have died, but state police said it was too early for casualty tolls as rescue operations were still under way.

The incident took place at around 11:00 am, some 30 minutes into the service, a survivor told local media from his Ibom Specialist Hospital bed.

"Suddenly, the roof from the middle fell on worshippers. The governor was quickly rescued. But others were not that lucky," he said. 

- 'Shocking incident' -

Akwa Ibom state governor Emmanuel Udom, who survived the disaster, declared two days of official mourning and said a ceremony honouring the victims would be held on Monday.

"We have never had such a shocking incident in the history of our dear state," he wrote on his Facebook page.

Police, soldiers, firefighters and volunteers joined with construction workers to dig through the rubble inside the building.

"Rescue team members are doing their best to rescue all the victims trapped at the collapsed building," police spokeswoman Cordelia Nwawe said.

Uyo's university hospital said all its doctors had been called in to manage the emergency, and the head of the regional branch of the Nigerian Medical Association called for a blood drive to help the victims.

"We still need more blood. You must not underestimate the number of lives that your blood donation will save," Aniekeme Aniefiok Uwah said in a statement.

- Growing number of evangelicals -

Police spokeswoman Nwawe officers were being "particularly attentive to keeping the situation under control and keeping looters from accessing the accident site."

President Muhammadu Buhari expressed "the deep sorrow of his family, the government and the entire people of Nigeria over the many deaths and injury recorded following the incident," his spokesman Garba Shehu said in a statement.

According to Gallup International, Nigeria is the world's second most religious country, with a notable rise in the number of evangelical churches.

In September 2014, 116 people including 84 South Africans, were killed in Lagos in the collapse of a church belonging to the famous televangelist TB Joshua.

The inquest verdict attributed the collapse of the six-storey guesthouse to structural failures and said it did not have planning permission. 

The preacher is due to face charges of criminal negligence but the trial has yet to start. 

The Mountain of Fire and Miracles Ministry, one of the largest Pentecostal churches in Nigeria, has one of the largest church auditoriums in the world with a seating capacity of 500,000.