Erdogan is locked in a power struggle with US-based Turkish Muslim cleric Fethullah Gulen, a former ally who he says is behind a stream of "fabricated" audio recordings posted on the Internet purportedly revealing graft in his inner circle.

"We are determined on this subject. We will not leave this nation at the mercy of YouTube and Facebook," Erdogan said in an interview late on Thursday with the Turkish broadcaster ATV.

"We will take the necessary steps in the strongest way."

Asked if the possible barring of these sites was included in planned measures, he said: "Included."

Erdogan says the release of his purported conversations is part of a campaign to discredit him and wreck his government, which has presided over more than a decade of strong economic growth and rising living standards in Turkey.

Gulen denies any involvement in the recordings and rejects allegations that he is using a network of proteges to try to influence politics in Turkey.

Five more recordings have appeared on YouTube this week, part of what Erdogan sees as a campaign to sully his ruling center-right AK Party before the March 30 municipal elections and a presidential poll due later this year.

In the latest recording, released on YouTube late on Thursday, Erdogan is purportedly heard suggesting the proprietor of Milliyet newspaper sack two journalists responsible for a front page story about Kurdish peace talk efforts.

Erdogan has signaled that a criminal investigation could be launched against Gulen's Hizmet movement.

Asked on Thursday night whether Turkey could seek an Interpol red notice for the extradition of Gulen from the United States, Erdogan said: "why not?"

BA/BA