Warri, Nigeria: At least 100 people were killed when a church roof in south-eastern Nigeria collapsed on Saturday, according to a hospital director and eyewitness reports.

Etete Peters, of the University of Uyo Teaching Hospital, said mortuaries were overflowing and the final death toll would go higher after the Reigners Bible Church in the Akwa Ibom state capital of Uyo collapsed during a service.

Local resident and photojournalist Ini Samuel agreed the death was high.

"At Uyo teaching hospital, where I am now, I could see over a hundred corpses, many are heaped on top off each other on the floor," he said. "Eyewitnesses also said yesterday corpses were packed in four each bag."

Gary Ubong, another resident, said the church's roof had collapsed on worshippers while a pastor was being consecrated as bishop in the presence of government officials.

"I saw more than 100 dead bodies brought out on loaders," said Mr Ubong, who had rushed to the scene after the accident. "I also went to two hospitals and saw heaps of dead bodies difficult to count."

However official death figures differed from first-hand reports, with state police spokeswoman Cordelia Nwawe saying 27 had been killed and 30 injured.

State emergency agency NEMA said in a statement that six people had been killed and 115 injured.

State governor Udom Emmanuel, who escaped unhurt from the church service, ordered the arrest of the building contractor, state news agency NAN reported.

Building collapses are frequent in the West African nation and often blamed by officials on lack of construction permits and the use of cheap materials amid widespread corruption.

Critics say Nigerian authorities tend to understate the death toll at such accidents or suicide bombings by the Boko Haram jihadist group in the north of the country.

During at gas plant blast in southern Nigeria a year ago, the presidency said "tens of people" had been killed while witnesses counted more than 100 bodies. Police had then just confirmed eight dead.

Reuters, AAP