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.
Arrest warrants were issued for 28 people at the TIB telecommunications authority and at TUBITAK, Turkey's Scientific and Technological Research Council, local media said.
Transport Minister Lutfi Elvan said Tuesday's operation was part of three investigations being carried out against TIB officials accused of involvement in illegal wiretapping.
A corruption investigation targeting Erdogan's inner circle which became public in December 2013 was based in part on wiretapped conversations, many of which were subsequently leaked on the Internet.
The government says Gulen was behind that investigation and had instigated it in an attempt to overthrow the government. A Turkish court issued an arrest warrant in December for the Muslim cleric, who has lived in self-imposed exile in Pennsylvania since 1999.
Erdogan responded to the investigation with a purge of the state apparatus, reassigning thousands of police and hundreds of judges and prosecutors deemed loyal to Gulen, in what his supporters said was a cleansing of the cleric's influence.
Turkey's Western allies have reacted with alarm to what they see as signs of erosion of the rule of law. Four prosecutors who initiated the graft inquiries have been suspended, the court cases dropped and government influence over the judiciary tightened.
Parliament was to vote on Tuesday on whether to commit four former ministers for trial over the corruption allegations, one of the last avenues of the investigation left open.