Istanbul: The Washington correspondent of a major Turkish newspaper said on Sunday he was under investigation for libel and allegedly insulting President Tayyip Erdogan, in what may be Turkey`s latest crackdown on media coverage critical of the authorities.

Tolga Tanis, a Washington-based reporter with the Hurriyet newspaper told Reuters he faces a probe from the Istanbul Chief Prosecutor`s Office after Erdogan`s lawyer filed a petition accusing him of libel and attempting to undermine Erdogan`s reputation in his book "POTUS and the Gentleman".

Published in March, the book examines relations between Washington and Ankara with a focus on U.S. President Barack Obama - "POTUS" is an acrononym for "President of the United States" - and Erdogan, sometimes called "the Gentleman" by supporters.

"I am critical of both Erdogan and Obama on several issues," Tanis told Reuters in an e-mail. "Though I don`t think that Obama is considering suing me for this book."

Reuters was unable to reach the prosecutor`s office or Erdogan`s lawyer for comment.

In what opponents see as part of a campaign to muzzle dissent, Erdogan has repeatedly berated news outlets including the New York Times and Turkish daily Hurriyet, while a prosecutor last month sought to shut two TV stations, seen as opposed to the government, on terrorism-related charges.

Erdogan rejects the notion that Turkey, which languishes near the bottom of international press freedom tables, has anything but a free media, declaring in January that Turkish journalists were freer than any in Europe.

Erdogan suffered a rare setback on June 7 when the governing AK Party he founded failed to win enough votes in a parliamentary election to remain in power as a single-party government.

He had hoped for a sweeping victory for the AKP, which would have allowed it to change the constitution and give him greater power.