Hundreds of Turkish nationalists have been protesting outside a controversial conference on the mass killings of Armenians under Ottoman rule.
Resistance to a free debate on the issue is still strong in Turkey
They chanted slogans and booed delegates entering Istanbul's Bilgi University for the two-day event.
The conference had been due to open on Friday, at another venue, but was stopped from doing so by a court order.
Debate of the killings has been taboo in Turkey but there is outside pressure for greater freedom of speech.
"Treason will not go unpunished" and "This is Turkey, love it or leave it," shouted the demonstrators.
"The Armenian genocide is an international lie," read a huge banner carried by members of the minor left-wing Workers' Party.
Armenians worldwide have been campaigning for decades for the deaths - thought to have been more than a million, around the time of WWI - to be recognised universally as genocide.
The conference discussing the issue was due to be held at Istanbul's Bosphorus University, but it was banned by an Istanbul court after complaints by nationalists that the historians behind it were "traitors".
The historians challenge official Turkish accounts of the killings, which give a much smaller death toll and link Armenian losses to civil strife in which many Turks also died.
The court ruling brought emotionally charged scenes on the Bosphorus campus on Friday, said the BBC's Sarah Rainsford in Istanbul.
Students, angry that the conference was cancelled, taped their mouths while small groups of nationalists gathered to condemn plans for the forum.
Bilgi University stepped in "in the name of freedom of expression and thought", said its president, Aydin Ugur.
Government leaders regretted the court ruling which "cast a shadow on the process of democratisation and freedoms", according to Prime Minister Recep Tayyip Erdogan.
"If we have confidence in our own beliefs, we should not fear freedom of thought," he told separate gathering of academics on Saturday.
EU enlargement commissioner Krisztina Nagy said Brussels strongly deplored the court's "attempt to prevent the Turkish society from discussing its history".
Turkey begins talks on joining the EU in two weeks' time.