A South Sudan bishop has criticised pastors apparently selling prayer and blessings to their church members.

Bishop Moses Deng Bol, of Wau Diocese, said the actions of these pastors had made him so angry that he felt unable to stay silent.

He warned churchgoers not to be fooled by the practice.

"Let us be clear – salvation is a free gift that no amount of money can buy," he said.

Paying for prayer, he said, was "contrary to the way God wants us to behave," and condemned the behaviour as an example of the "prosperity Gospel", which espouses the idea that Christians will receive financial blessings and material success as a result of their faith.

"It makes me so mad that because they lust for money, people that have been trusted to lead in faith are taking advantage of those that cannot understand the message of Jesus properly," the bishop said.

In a message to his diocese, he pointed to passages in from Romans, 1 Timothy and Ephesians, which show that by the grace of God we have been given Jesus as a sacrifice for our salvation.

"Why pay a heretic when all you have to do is just ask God, through Jesus?" he said.

"God loves us so much. If you pay for someone to pray for you, or to bless you, you are wasting your money."

Bishop Deng Bol has called for prayer for the church leaders in question, calling them "misguided and greedy", and asking that "God will open their eyes to see that what they are doing is not acceptable".

"Then they may stop this disgraceful practice and return to the true faith that they were freely given; as a gift from the almighty God that loves them."