Turkish police have detained at least 18 academics who signed a petition criticising military operations in the largely Kurdish south-east.
Fifteen were later released after questioning, the state-run Anadolu agency reported.
The academics are accused of engaging in "terrorist propaganda" and insulting the state.
But the detentions have rekindled concerns about freedom of expression in Turkey, analysts say.
The 15 released are lecturers at Kocaeli University in north-western Turkey, Anadolu reported. The three others are from Uludag University in Bursa province.
But the number of academics arrested could be higher, the Reuters news agency reported.
The declaration, signed by more than 1,000 academics in Turkey and abroad, calls on the government to halt "massacres" in the south-east.
The signatories stated that they refused to be "a party to the crime" and called for the resumption of peace efforts with the rebels.
The document was prompted by a Turkish government offensive against the outlawed separatist group Kurdistan Workers' Party, or PKK, that includes military operations and curfews.
But President Erdogan accused those who signed the document - including renowned international linguist and philosopher Noam Chomsky - of engaging in "terrorist propaganda" on behalf of the PKK.
The PKK is considered a terrorist group by Turkey and its Western allies and has fought a 30-year separatist insurgency in south-eastern Turkey that has killed tens of thousands of people.
Mr Erdogan accused the academics of being biased against the state and denounced them for failing to condemn rebel violence. He urged the judiciary to take action against their "treachery".
The Turkish opposition and the US ambassador to Turkey criticised prosecutors' orders to investigate and allow home searches of academics after Mr Erdogan's remarks.
US ambassador John Bass warned of the "pressure having a chilling effect on legitimate political discourse across Turkish society regarding the sources and solutions to the ongoing violence".
There have been repeated clashes between PKK separatists and the Turkish army in recent months, and the violence has recently escalated.
On Thursday a car bomb which the authorities said was planted by the rebels detonated outside a police headquarters in Cinar district. Six people were killed.
The government has imposed a series of curfews in the south-east while militants have erected barricades, dug trenches and used explosives to keep the authorities away.
Since August, human rights activists say 170 civilians have lost their lives in areas under curfew and thousands have been displaced, but Turkish officials have denied that the offensive has endangered or killed civilians.
The hashtag #1128katil (1,128 killers) was trending in Turkey on Thursday, particularly among government and nationalist supporters, apparently in reference to the academics.