Most of the scholars were from Kocaeli University in northwestern Turkey and were detained in early-morning raids on their homes, the semiofficial news agency Anadolu reported. By Friday evening, all had been released, according to Turkish news media reports.

All 27 scholars were among more than 1,000 academics from 90 Turkish universities who signed a public statement, "We Won’t Be a Party to This Crime,” that urged the government in Ankara, the capital, to end the "deliberate massacre” of Kurds caught in clashes between Turkish security forces and militants of the Kurdistan Workers’ Party, or P.K.K.

The petition angered President Recep Tayyip Erdogan, who denounced the group — and foreign scholars who signed the document, including the linguist and philosopher Noam Chomsky — in a televised speech on Tuesday. Mr. Erdogan accused them of "treason” and of forming a "fifth column” of foreign powers trying to undermine Turkey’s national security.

"Unfortunately, these so-called academics claim that the state is carrying out a massacre,” Mr. Erdogan said in his speech, which came shortly after a suicide bombing that killed 10 German tourists in the historic heart of Istanbul, for which the Islamic State claimed responsibility. "Hey, you so-called intellectuals: You are dark people. You are not intellectuals.”

Mr. Erdogan called on Mr. Chomsky and other scholars to visit southeastern Turkey to get a "true picture” of the events taking place there.

"They should see with their eyes whether the problem is a violation by the state or the hijacking of our citizens’ rights and freedoms by the terrorist organization,” he said, referring to the Kurdistan Workers’ Party. On Thursday, the government formally began an investigation of the scholars.

No details were available about the investigation, but if it leads to a trial the academics could face one to five years in jail if convicted.

The detentions have deepened concerns over freedom of expression in Turkey under Mr. Erdogan’s leadership, and analysts say that the latest crackdown on academics is intended to muzzle debate and to curb academic freedoms.

"The campaign against academics this week certainly targets a new group and has very serious consequences for academic freedom in Turkey, as well as free speech,” said Emma Sinclair-Webb, a senior Turkey researcher at Human Rights Watch. "There are concerns for the physical safety of some academics in provincial universities after being targeted in such a way.”

(The petition has even drawn criticism from a notorious organized-crime boss, Sedat Peker, who is known for his nationalist viewpoints. "We will spill your blood, and we will take shower with your blood,” he said in a statement on his website.)

Several scholars, reached by telephone on Friday, declined to comment on the detentions for fear of reprisal. But many of them said they stood by their signatures.

"Freedom of expression was already very limited in Turkey,” said Esra Ozyurek, chairwoman of Contemporary Turkish Studies at the London School of Economics, who signed the petition. "It is very difficult to find a venue for oppositional voices, and as we see voicing dissent comes with a very high price. Even demanding peace is easily criminalized.”

Ms. Ozyurek said that she expected that she and others who signed the petition would face similar charges.

Prime Minister Ahmet Davutoglu, a political scientist and former university professor, also lashed out at the scholars who signed the petition.

"Being an intellectual and defending democracy is first of all possible by defending democratic methods,” Mr. Davutoglu said. "Why are you aligning behind this terrorist organization?”

The United States ambassador to Turkey, John R. Bass, criticized the arrests, saying they would have a "chilling effect on legitimate political discourse” about the violence in southeastern Turkey.

"In democratic societies, it is imperative that citizens have the opportunity to express their views, even controversial or unpopular ones,” he said in a statement on Twitter. "Expressions of concern about violence do not equal support for terrorism. Criticism of government does not equal treason.”

Violence has surged in Turkey’s volatile southeast since the renewal of a decades-old conflict between Kurdish militants and the Turkish state that has claimed more than 40,000 lives.

The Turkish military started a major counterinsurgency campaign last month, imposing round-the-clock curfews in Kurdish areas to drive Kurdish militants out of their strongholds. Rights groups say that nearly 200 civilians have been killed in the violence.

 

(New York Times)