The roof of a church collapsed during mass near the eastern South African city of Durban, killing 13 people and injuring at least 16, officials said Friday.

"The roof of the building collapsed because of heavy rains last night ... at this point we have a total of 13 fatalities," said Lennox Mabaso, spokesman for the provincial traditional affairs department.

"Such a tragedy. 13 fatalities 16 people treated by paramedics," tweeted Robert McKenzie, spokesman for Kwa-Zulu Natal province's emergency services. He said heavy rainfall may have been to blame for the collapse Thursday night in the town of Dlangubo.

The report says the collapse at the Pentecostal church occurred as an Easter season service was underway.

"There was a strong storm at the time but we can't be totally sure why the wall collapsed until the police are done with their investigations," said McKenzie.

Pictures of the scene on the emergency services' Twitter page showed bricks and piles of debris strewn across the church floor, with pipes and pillars hanging from higher parts of the building.

Dozens of local people, dazed by the tragedy, spent hours pacing the ruined interior of the building.

"There was no (mobile phone) network so I just ran to the police station and called the police, they responded very quickly and they helped us," Pastor P.Y. Sibiya told AFP.

Zwelihle Dhlamini, who lost a colleague in the tragedy, told AFP of his shock.

"Right now, I cannot believe what has happened. I still have not recovered from the shock and so are our colleagues. They are still calling me, they are still sending messages as if something is going to change."

'Labour Minister Mildred Oliphant, a member of the church, said it was difficult to come to terms with the disaster, "but we know God has his own reasons.

"I was going to attend the church today. Probably by the end of next week, we will know exactly whether the structure was properly built or what were the challenges about the structure before we say anything."

Police have meanwhile launched an investigation while other congregations joined authorities in passing on condolences.

"We have been praying for them, our sincere condolences to the families. As Christians, we pray for one another in bad and good times. Indeed those people of Empangeni are in our prayers," said South African Council of Churches (SACC) provincial deputy chairperson Father Mlungisi Ntsele.