FILE PHOTO: Serpil Kemalbay, newly elected co-chairwoman of the Pro-Kurdish Peoples' Democratic Party (HDP), speaks during her party's extraordinary congress in Ankara, Turkey, May 20, 2017. REUTERS/Stringer

ISTANBUL (Reuters) - Turkey has ordered the arrest of 17 people including the co-leader of the main pro-Kurdish political party over opposition to the military’s offensive in Syria, the state-run Anadolu news agency said on Friday.

Since the launch of the campaign in northwest Syria’s Afrin nearly three weeks ago, authorities have said they would arrest those who criticize or oppose it. So far, some 600 people have been detained for protests or for social media posts against the offensive.

Anadolu cited the Ankara prosecutor’s office as saying the 17 suspects now facing arrest were accused of seeking to stir street protests and clashes under the guise of opposition to the Afrin offensive.

Among them were Serpil Kemalbay, the co-leader of the Peoples’ Democratic Party (HDP), it said. The HDP, parliament’s second-largest opposition party, is the only major political party to oppose the campaign - dubbed “Operation Olive Branch” - against the Kurdish YPG militia in Afrin.

The party is scheduled to hold its annual congress in Ankara on Sunday.

The HDP’s other co-leader, Selahattin Demirtas, is in jail over alleged links to Kurdish militants and is among many leading members of the party imprisoned on similar charges, which they have denied.

The YPG is designated by Ankara as a terrorist group and an extension of the Kurdistan Workers Party (PKK), which has waged a three-decade insurgency on Turkish soil in which more than 40,000 people have been killed.

President Tayyip Erdogan said on Thursday that Turkey will strip the word “Turkish” from the name of its main medical association after the group publicly opposed the campaign.