Millions are flooding to join Pentecostal churches in Africa where vows of miraculous healing and promises of pending fortunes are attracting swathes of the continent's sick and poor.

In particular, the West African nation of Nigeria is experiencing the fastest growth in Christianity in Africa with Pentecostal churches playing a large role in this development.

Nigeria is estimated to have the world's third largest population of Pentecostals with 3.9 million members, following Brazil with 24 million and the United States with about six million adherents, according to the World Christian database.

But what makes Nigeria - as well as other African nations unique - is the heavy emphasis - moreso than Pentecostalism in the West - on miracles, which incorporate traditional African beliefs, and material blessings.

"There are so many people who could have had bigger and better lives, but they could not achieve their destiny, because there was no one to lead them with a vision," said Ejiah Ndifon, a Nigerian self-declared prophet, according to Germany's media outlet Deutsche Welle last Friday.

Ndifon was formerly an engineer before founding the Pentecostal church Royal Kingdom Citizen International, based on promises of cures from poverty and disease.

"Royal Kingdom Citizen offers this guidance, and brings people together with God," he said.

African Pentecostal followers believe the Holy Spirit changes lives so that sickness and calamity only befall non-believers.

"Old superstitions, which were marginalised by more mainstream Christian missionaries, have come around full circle," said Erhard Kamphausen, head of the academy of missions at the University of Hamburg, according to the Deutsche Welle. "Africans believe in miracles and witchcraft."

In addition, Pentecostal preachers and churches have come under criticism for emphasising that adherents must donate to secure their good fortune.

Ayimah Hondeh, a member of Redeemed Christian Church of God in Lagos, said her pastor told members that God's blessing is not guaranteed year to year and followers must pray twice as hard and double donations to the church.

"I quadrupled my contribution to the collection plate every Sunday," said Hondeh.

Yet the Pentecostal message is not welcomed by all Christian leaders in Africa.

The Rev Dr Nyansako-ni-Nku, president of the All Africa Conference of Churches, has warned people to beware of churches that exploit people in the name of the Gospel. The AACC is a fellowship of 169 churches and Christian councils spanning 39 African countries.

The African church head urged mainline churches to "rescue" people who are being lured by controversial African Pentecostal churches, which he described as a "disease".

All over Africa, there is a surge of "one disease called Pentecostalism", he said, according to AACC. Nyansako repeatedly noted the rapid growth of the Pentecostal church and the call for mainline churches to protect vulnerable people that are being exploited by Pentecostal prosperity churches.

He urged member churches to undergo a thorough social audit to give them credibility to speak against church corruption.

"This means the church must take its mandate very seriously as we are the mantle of the continent of Africa and if we let the continent down, it would be a disaster for everybody," Nyansako said.

Overall, there are an estimated 400 million Christians in Africa.

Pentecostals today represent around 12 per cent of Africa's population, or about 107 million, according to the World Christian Database. Charismatic members of non-Pentecostal denominations make up another 5 per cent of the population, or about 40 million. The proportion of Pentecostals and Charismatics combined was less than 5 per cent just over three decades ago.