The Turkish prosecutor responsible for trying US pastor Andrew Brunson, has been replaced, leading to hopes his long-running case might be taking a different turn.

Brunson, a missionary pastor in Izmir imprisoned on terrorism charges widely assumed to be false, has been moved from prison to house arrest.

According to World Watch Monitor, his prosecutor was substituted at the beginning last week of Turkey's new judicial year.

Justice Minister Abdulhamit Gul dismissed the transfer simply as a 'routine procedure' with no particular significance, referring to Turkey's common practice of changing judges and prosecutors mid-way through the trial process.

However, the replacement of Berkant Karakay was described by Brunson's lawyer as a move that could bring positive change in the pastor's highly disputed case.

Ismail Cem Halavurt told Reuters it would be wrong to expect the change to result in the pastor's release. However, he said: 'He [Karakaay] has constantly added fresh testimonies from anonymous witnesses who had nothing to do with my client. Now his removal might be a sign that the will about this case is changing.

'But it is not right to say that [Brunson] might be freed based on this development. We will have to wait and see.'

Brunson's third hearing was held on July 18, after which he was transferred to house arrest. He is due in court again on October 12.

His case has heightened tensions between the US and Turkey, an ally and fellow NATO member, with US officials hitting Turkey with sanctions of his continued detention.

President Donald Trump said: 'I think it's very sad what Turkey is doing. I think they are making a terrible mistake. There will be no concessions.'

Turkey's economy has suffered because of the standoff, with sharp falls in the value of the lira.

Brunson faces 35 years in prison if he is convicted.