Hundreds of Muslim refugees are converting to Christianity in a Berlin church.

Pastor Gottfried Martens has seen his congregation at the evangelical Trinity Church grow from 150 to more than 600 in just two years, describing the number of conversions as a 'miracle', according to Associated Press.

One of these converts is Mohammed Ali Zonoobi, a carpenter from Shiraz, Iran, who was recently baptised.

Zanoobi was introduced to the Bible aged 18 and attended secret services in Iran. When several of his Christian friends were arrested, he fled with his wife and two children to Germany.

For Zonoobi and his wife Afsaneh their baptism marks a new beginning. "Now we are free and can be ourselves," she said. "Most important, I am so happy that our children will have a good future here and can get a good education in Germany."

Zanoobi is one of hundreds of mostly Iranian and Afghan asylum seekers who have been baptised at Trinity Church.

However, there are concerns that some are not genuine converts, rather professing a Christian faith to boost chances of staying in the country.

In Afghanistan and Iran conversion to Christianity from Islam is punishable by death or imprisonment.

Congregation member Vesam Heydari told AP, "The majority of Iranians here are not converting out of belief... They only want to stay in Germany."

Martens acknowledges this possibility, but says once in church, most people do engage and that around 90 per cent of converts continue attending after they have been baptised.

"I know there are – again and again – people coming here because they have some kind of hope regarding their asylum," Martens said. "I am inviting them to join us because I know that whoever comes here will not be left unchanged."

German Chancellor Angela Merkel has said Islam 'belongs in Germany' and that claiming to be Christian does not guarantee a successful asylum application.