Turkish police on Friday arrested 21 academics for terror propaganda over a petition denouncing military operations against Kurdish rebels which was severely criticised by President Recep Tayyip Erdogan, Turkish media said.

According to Anatolia news agency, with prosecutor’s order, police launched a vast investigation into over 1,200 academics from 90 Turkish universities. They were accused of “insulting the state” and engaging in “terrorist propaganda” by signing the declaration.

About 1,200 people have signed the petition entitled “We won’t be a party to this crime” which urges the government to stop “its deliberate massacres and deportation of Kurdish and other peoples in the region.”

Erdogan on Thursday accused the signatories of “treason”. “You are people in the dark. You are not intellectuals!” he said adding that “All you want is to stir this country up”.

Among the signatories are American linguist Noam Chomsky and Slovenian philosopher Slavoj Zizek.