A Turkish court today ordered access to YouTube to be blocked because of videos allegedly insulting the founder of modern Turkey, Mustafa Kemal Ataturk.
Paul Doany, head of Turk Telekom, Turkey's largest telecommunications provider, said his company had enforced the ban immediately.
"We are not in the position of saying that what YouTube did was an insult, that it was right or wrong," Mr Doany said in remarks to the state-run Anatolia news agency. "A court decision was proposed to us, and we are doing what that court decision says."
The vast majority of Turkish internet users use Turk Telekom, a former state-run monopoly that was privatised in 2005.
Visitors to the YouTube site from Turkey were greeted with the message: "Access to this site has been blocked by a court decision!"
And a message in both Turkish and English at the bottom of the page read: "Access to YouTube.com site has been suspended in accordance with decision no: 2007/384 dated 06.03.2007 of Istanbul First Criminal Peace Court."
Mr Doany said Turk Telekom would allow access to the popular video-sharing site again if the court decision were rescinded. Access from Turkey may be possible through other service providers, he said.
Over the past week, Turkish media publicised what some called a "virtual war" between Greeks and Turks on YouTube, with people from each side posting videos to belittle and berate the other.
The video prompting the ban allegedly said Ataturk and the Turkish people were homosexuals, according to news reports. The CNN-Turk Web site featured a link allowing Turks to complain directly by email to YouTube about the "insult."
On its front page on Wednesday, the newspaper Hurriyet said thousands of people had written to YouTube, and that the Ataturk videos had been removed from the site. "YouTube got the message," the headline said.
Insulting Ataturk or "Turkishness" is a crime in Turkey punishable by prison.
Turkey, which hopes to join the European Union, has been roundly condemned for not doing enough to curb extreme nationalist sentiments and to protect freedom of expression.