The anonymous posting followed similar releases on social media in recent weeks which Erdogan has cast as a plot orchestrated by political enemies to unseat him ahead of March 30 elections. But it took the campaign to a higher level, impinging on the most sensitive areas of national security.
An anonymous YouTube account posted what it presented as a recording of intelligence chief Hakan Fidan discussing possible military operations in Syria with Foreign Minister Ahmet Davutoglu, Deputy Chief of military Staff Yasar Guler and other top officials.
"They even leaked a national security meeting. This is villainous, this is dishonesty...Who are you serving by doing audio surveillance of such an important meeting?" Erdogan declared before supporters at a rally ahead of March 30 local polls that will be a key test of his support amid a corruption scandal.
The foreign ministry described the leak as a "wretched attack" on national security and said those behind it would receive the heaviest punishment. It said some sections of the recording had been manipulated. Reuters was unable to verify the authenticity of the recordings.
The conversation appears to centre on a possible operation to secure the tomb of Suleyman Shah, grandfather of the founder of the Ottoman Empire, in an area of northern Syria largely controlled by militant Islamists.
Ankara regards the tomb as sovereign Turkish territory under a treaty signed with France in 1921, when Syria was under French rule. About two dozen Turkish special forces soldiers permanently guard it.
"NATIONAL SECURITY ISSUE"
Turkey threatened two weeks ago to retaliate for any attack on the tomb following clashes between militants of the Islamic State of Iraq and the Levant (ISIL), an al Qaeda breakaway group, and rival rebel groups in the area, east of Aleppo near the Turkish border.
"An operation against ISIL has international legitimacy. We will define it as al Qaeda. There are no issues on the al Qaeda framework. When it comes to the Suleyman Shah tomb, it's about the protection of national soil," a voice presented as that of foreign ministry undersecretary Feridun Sinirlioglu says.
When the discussion turns to the need to justify such an operation, the voice purportedly of Fidan says: "Justification can be created. The matter is to create the will."
The Turkish telecoms authority TIB said it had taken an "administrative measure" against YouTube, a week after it blocked access to microblogging site Twitter.
A source in Erdogan's office said the video sharing service was blocked as a precaution after the voice recordings created a "national security issue" and said it may lift the ban if YouTube agreed to remove the content.
Google said it was looking into reports that some users in Turkey were unable to access its video-sharing site YouTube, saying there was no technical problem on its side.
