At least nine leading pro-Kurdish politicians went on a hunger strike on Wednesday in protest of Turkish military operations in the Afrin region of Syria, the Birgün daily reported.

Among the strikers are the Peoples’ Democratic Party (HDP) Co-Chair Figen Yüksekdağ, the Democratic Regions Party (DBP) Co-chairperson Sebahat Tuncel and the deputy co-chair of the HDP, Aysel Tuğluk.

The Turkish Armed Forces backed by armored vehicles, special forces and infantry regiments have advanced five kilometers inside Afrin, which is controlled by the PYD.

Since early Sunday morning, Turkish public prosecutor’s offices issued detention warrants for at least 41 people accross Turkey for criticizing the military operation.

Turkey views the PYD as the Syrian extension of the PKK.

Turkey has stepped up its crackdown on Kurdish politicians since 2016. Trustees have been appointed to dozens of municipalities in the country’s predominantly Kurdish Southeast, while hundreds of local Kurdish politicians have been arrested on terror charges.

Ten HDP deputies including Co-chairperson Selahattin Demirtaş and former Co-chairperson Figen Yüksekdağ are still in prison.

The Ankara Chief Public Prosecutor’s Office earlier on Sunday announced in a statement that investigations had been launched into individuals who have called on people to take to the streets to protest Turkey’s operations targeting Afrin.

The Ankara Chief Public Prosecutor’s Office on Sunday launched an investigation into pro-Kurdish Peoples’ Democratic Party (HDP) deputies Ayhan Bilgen and Nadir Yıldırım for “incitement of hatred and hostility” through their critical messages on Twitter over Turkish military operation in Afrin.

President Recep Tayyip Erdoğan on Sunday warned the HDP not to take to the streets to protest the operation in Afrin: “You are being closely followed. If you try to take to the streets, know that our security forces will be at your neck.”

“If anyone is in the streets upon calls [from the HDP], they will pay dearly for it. This is a national fight, and whoever opposes us will be crushed.” Erdoğan added.