Reuters: Turkish police detained 23 people suspected of a role in illegal wiretapping on Tuesday in a move local media said was aimed at supporters of President Tayyip Erdogan’s ally-turned-foe, U.S.-based cleric Fethullah Gulen.

Ankara prosecutors are investigating claims of wiretapping targeting Erdogan, Prime Minister Ahmet Davutoglu, the head of the armed forces and other top officials. The prosecutor’s office was not available for comment.

Separately, the interior ministry replaced police chiefs in 21 provinces, according to an announcement published in Turkey’s Official Gazette. It was not immediately clear why they were being replaced.

Broadcasters including CNN Turk said the raids, in four provinces including Ankara, were against the “parallel structure”, the term Erdogan uses to refer to Gulen’s supporters in the judiciary, police and other institutions.