Turkey's prime minister and the EU have criticised a court ruling ordering the cancellation of a conference about the 1915 killing of thousands of Armenians.
Armenians are still haunted by the killings of 1915
The conference of academics was to debate Turkey's official approach to the disputed events of 90 years ago.
Prime Minister Recep Tayyip Erdogan said stopping a meeting, when it was not clear what would be discussed, had nothing to do with democracy.
An EU spokeswoman said it was a bid to stop Turkey discussing its history.
The Turkish court ruling on Thursday, which followed a complaint by nationalists, comes just days before Turkey is due to start talks on joining the European Union.
Discussing the 1915 killings has long been a taboo in Turkey.
Armenia accuses the then Ottoman rulers of carrying out a "genocide" - a claim backed by 15 countries, including France, Switzerland, Russia and Argentina.
But Turkey disputes the charge, saying that a few hundred thousand died and that the deaths occurred in a civil war in which many Turks were also killed.
Mr Erdogan questioned the court's ruling.
"The court has cast a shadow on the process of democratisation and freedoms in my country," he said.
Foreign Minister Abdullah Gul agreed, saying the ruling was the outcome of efforts by opponents of the country's EU bid.
"As 3 October is approaching, those at home and abroad who want to obstruct us are making their last efforts... There are few nations that can inflict such damage on themselves," he said in New York, Anatolia news agency reported.
European Commission spokeswoman Krisztina Nagy said: "The absence of legal motivations and the [timing] of this decision a day before the conference looks like yet another provocation."
The first attempt to stage the debate, in May, was abandoned after Turkey's justice minister accused organisers of stabbing Turkey in the back.
The BBC's Sarah Rainsford in Istanbul says it was illegal even to discuss the issue until a very recent reform inspired by Turkey's bid for membership of the European Union.
The university has the right of appeal, but lawyers say there is now little to no chance the ground-breaking debate can go ahead as planned on Friday.