The EU on Thursday decried the detention of university students in Turkey and the use of anti-LGBT "hate speech" after President Recep Tayyip Erdogan lashed out at youth-driven protests.
"The European Union is seriously concerned over the negative developments in Turkey in the areas of the rule of law, human rights and the judiciary," a spokesman for foreign policy chief Josep Borrell said in a statement.
It called the detention of student demonstrators and a decision by authorities to ban rallies around Istanbul's elite Bogazici University "a deeply worrying development".
"We call on Turkey to respect its national and international obligations and to release those arbitrarily detained for exercising their right to peaceful assembly over the last weeks," the statement said.
More than 300 students and their supporters were detained in Istanbul and the capital Ankara in increasingly violent and politically-charged altercations with the police this week.
The protests first erupted after Erdogan named a party loyalist as head of Bogazici University at the start of the year.
The appointment created a stir because students saw it as part of Erdogan's broader effort to centralise control over most facets of Turks' daily lives.
Erdogan compared the protesters to "terrorists" on Wednesday in one of his most heated attacks to date against a movement that threatens to grow into a serious challenge to his 18 years in power.
The dispute over the rector intensified after protesters hung a poster near his office depicting Islam's holiest site covered in LGBT imagery last week.
The scandal over the poster thrust the LGBT movement to the centre of Turkish politics and saw it come under growing attack from top officials.
"The LGBT, there is no such thing," Erdogan insisted on Wednesday. "This country is ... moral, and it will walk to the future with these values."
That came after Interior Minister Suleyman Soylu tweeted on Saturday that "four LGBT freaks" had been detained over the poster and Bogazici University's LGBT club was disbanded.
"Hate speech displayed by high-level officials against LGBTI students during these events and the closing of a LGBTI association is unacceptable," the EU statement said.
The crackdown on the protests threatens to derail a push by Turkey to rebuild tattered ties with the EU after tensions hit new levels last year over Ankara's actions in the east Mediterranean.
The US has also condemned the detentions and anti-LGBT rhetoric.