Turkey's 10 million Twitter users have been unable to access the site from late last night, following the PMs vow to 'eradicate it'.
The victim of a stabbing attack in Turkey has branded his attackers "disgusting", saying he owes his life to the "best surgeon in Turkey".
Anti-government protesters and police have been fighting a running battle for control of Istanbul's Taksim Square on an 11th day of clashes.
A court has lifted the ban on YouTube in Turkey but 15 videos will continue to be blocked, Ankara court documents show.
Officials had blocked access to the site as a "precaution" after voice recordings purportedly of senior officials discussing a potential operation in Syria were posted on the video-sharing website.
Turkey has lifted a ban on Twitter after a constitutional court ruled the block violated the right to free expression, an official in the prime minister's office told the Reuters news agency.
Turkish Prime Minister Tayyip Erdogan declared victory in local polls that had become a referendum on his rule and said he would "enter the lair" of enemies who have accused him of corruption and leaked state secrets. "They will pay for this," he said.
Erdogan spoke from a balcony at his AK Party headquarters to thousands of cheering supporters as early results showed it winning some 44-46% of the vote, and the opposition CHP trailing with 23-28%.
Erdogan accuses a US-based Islamic cleric, a former ally, of mounting a smear campaign using a network of followers in the police force to concoct a corruption case against him. In response he has purged the police force of thousands of members.
Six people have been killed in clashes between groups backing rival candidates in Turkey's municipal elections, Reuters reported.
Security officials said four people were killed in a gun fight between two families in the eastern province of Sanliurfa, located near Syria's border.
In Hatay province, which also borders Syria, two people died during a gunbattle between relatives of two candidates, the officials said.
The candidates were not party-affiliated, the report added.
Twitter users inside Turkey have been expressing their frustration at the reported YouTube ban.
Google said it was looking into reports that users in Turkey are unable to access YouTube. IN a statement, it said there was "no technical issue" on their side, and that they were looking into the problem.
We're seeing reports that some users are not able to access YouTube in Turkey. There is no technical issue on our side and we're looking into the situation.
Turkey has blocked access to YouTube as a "precaution" officials said, after voice recordings purportedly of senior officials discussing a potential operation in Syria created a "national security issue", a source at the prime minister's office told Reuters.
The source said Turkey was in talks with YouTube and may lift the ban if the content was removed.
The comes less than a week after the Turkish prime minister blocked access to Twitter after vowing to "eradicate" the social media site.
Prime Minister Tayyip Erdogan threatened to ban Facebook and Youtube earlier in the month after wiretapped audio recordings linking him to allegations of corruption damaged the government's reputation ahead of local elections.
Mr Erdogan insists the recordings, widely shared on Facebook, YouTube and Twitter, were fabrications.
Twitter says it has filed petitions in Turkish courts to challenge the ban on its service.
In a statement the social network said:
"It’s now been six days since the Turkish government blocked access to Twitter. Throughout this time, we’ve been engaged in discussion with Turkish authorities ... But still, the millions of people in Turkey who turn to Twitter to make their voices heard are being kept from doing just that.
"So today, we filed petitions for lawsuits."
The Turkish Prime Minister has congratulated his armed forces after they shot down a Syrian plane, saying: "If you violate our border, our slap will be hard."
Recep Tayyip Erdogan said the plane violated Turkish air space and added: "I congratulate firstly our Chief of General Staff, and our pilots. I congratulate our Air Forces."
Syrian state television has quoted a military official saying the plane shot down by Turkey was pursuing rebel fighters within Syria's own territory.
The Turkish Prime Minister has said the jet was shot down because it had violated Turkish air space.