Turkish police detained early Wednesday four suspects in previously determined addresses linked with PKK terror organization in Istanbul, Ankara, and Kars provinces as part of the ongoing investigation launched after the terror attack in capital Ankara on March 13.

In the wide-range operations launched simultaneously, four suspects were detained for alleged linkage to the March 13 Ankara attack, including two in Ankara, one in Istanbul and one in the eastern Kars province.The Ankara attack on March 13 was claimed by PKK terror organization.

The two suspects detained in Ankara were put on routine health check prior to being sent to Ankara Police Headquarters, while the other two are also being sent to Ankara.

More arrests are expected as part of the large scale investigation.The PKK -- listed as a terrorist organization by Turkey, the U.S. and the EU - resumed its 30-year armed campaign against the Turkish state in July 2015. Since then, more than 430 security personnel have been martyred and more than 3,800 PKK terrorists killed.