Rebels of the Kurdistan Workers' Party (PKK) seized the climbers, part of a group of 13 mountaineers, as they were ascending the mountain in Agri province, provincial governor Mehmet Cetin told Anatolia news agency.
Five rebels came to the climbers' camp located at an altitude of 3,200 metres and kidnapped three persons in protest at the German government's crackdown on PKK-affiliated bodies and its supporters in Germany, Cetin said.
Turkish paramilitary troops have launched an operation to rescue the climbers while the other hikers were brought down from the mountain. Officials from the German embassy were not immediately available for comment.
The PKK, which is listed as a terrorist group by Ankara and several Western countries, has been fighting for self-rule in Turkey's Kurdish-populated east and southeast since 1984. The conflict has claimed more than 37,000 lives.
Mount Ararat, situated close to the Iranian and Armenian borders, is the highest mountain in Turkey at 5,137 metres (16,853 feet) and is believed by many to be the final resting place of the Biblical Noah's Ark.