ISTANBUL (REUTERS) - A Turkish court ordered the arrest of 21 police officers on Sunday as part of an investigation into the illegal wiretapping of politicians, civil servants and businessmen, the Dogan News Agency reported.

Raids began in several cities as prosecutors enforced the court order, privately owned Dogan said, the latest step in President Tayyip Erdogan's campaign against supporters of his ally turned arch-foe, US-based Muslim cleric Fethullah Gulen.

Prosecutors were not immediately available for comment.

Scores of police officers have already been detained as part of the investigation since the middle of last year.

Erdogan accuses Gulen of setting up a "parallel state"within the Turkish administration and of trying to topple him, blaming Gulen's supporters within the police and judiciary for a corruption inquiry that rocked the government late in 2013.

In the course of the scandal, wiretap recordings of senior officials leaked onto the Internet. Thousands of police officers, judges and prosecutors have since been removed from their posts.

In December, a Turkish court issued an arrest warrant for Gulen on suspicion of heading a criminal organisation and last week Turkey revoked his passport. Gulen, who lives in self-imposed exile in the United States, denies plotting against the government.