The mayor of Turkey's eastern city of Bitlis was arrested on Thursday as part of a counterterrorism investigation, a source in the police said.

Teams from the Bitlis Police Department's anti-terror branch arrested Mayor Hüseyin Olan along with Nevin Daşdemir Dağkıran, an alderman in the municipality, as part of an anti-PKK probe, confirmed the source, who spoke on condition of anonymity. Police also conducted a search of the municipality building.

Thursday's detentions are the latest in a series of investigations into elected officials of Turkish municipalities.

On Nov. 17, the mayor of Tunceli, Mehmet Ali Bul, Van Mayor Bekir Kaya from the Democratic Regions Party (DBP), and four other municipality officials were arrested.

On Nov. 21, two suspended mayors, Ahmet Türk from Mardin province and Emin Irmak from the province's Artuklu district, were also detained.

Earlier this month, 13 lawmakers from the Peoples' Democratic Party (HDP) were arrested. Ten, including co-leaders Selahattin Demirtaş and Figen Yüksekdağ, remain in custody awaiting trial on terrorism-related charges.

In October, the DBP co-mayors of Diyarbakir, the largest city in the southeast, were arrested and jailed pending trial on similar charges.

The PKK, listed as a terrorist organization by Turkey, the United States and the EU, resumed its decades-old armed campaign in July last year and has been responsible for the deaths of more than 1,100 security force members and civilians, including women and children.