Istanbul police raided the pro-Kurdish Peoples’ Democratic Party’s (HDP) local office in Sancaktepe district and detained at least 18 people on Sunday.

At least 18 people including two party executives were detained during the raid, media reported. Police carried out the operation upon the complaint that there was “outlawed placards” in Sancaktepe office, according to media.

A Turkish flag was drawn on the walls of the office, according to HDP’s tweet posted following the raid.

Turkey has stepped up its crackdown on Kurdish politicians recently. 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 along with HDP parliamentarians including the party’s former co-chairs Figen Yüksekdağ and Selahattin Demirtaş.