Turkey's state-run Anadolu Agency says prosecutors have launched an investigation into more than 1,000 academics for insulting the state and engaging in "terrorist propaganda" by signing a declaration denouncing military operations against Kurdish rebels in southeast Turkey.

Thursday's move by prosecutors' in Istanbul is seen as part of the government's ever-growing crackdown on dissenting voices.

It came after Prime Minister Recep Tayyip Erdogan severely criticized the signatories, including famed linguist Noam Chomsky, and called on the judiciary to act against the "treachery."

In the declaration, about 1,200 academics called on Turkey to halt "massacres" and said they refused to be "a party to the crime."

Earlier on Thursday, Duzce University in northwest Turkey fired a sociology lecturer for signing the declaration, the private Dogan news agency said.