Filmed by Anadolu Agency, the tunnel network was apparently used by the terrorist group as shelter against jet strikes and other heavy artillery fire amid Turkey’s counter-terrorist operations.
The tunnels also linked the so-called terrorist command centers with strategic points and surveillance towers, according to local sources who spoke on condition of anonymity due to security concerns.
In the footage, electrical wiring and living areas can be seen in the tunnels and shelters.
Also found in the shelters were diaries of terrorists written in Turkish and Kurdish as well as many political documents and images of Abdullah Ocalan, the terrorist head of the PKK, the parent group of the terrorist PYD/PKK -- underlining the close links between the terror groups.
On Jan. 20, Turkey launched Operation Olive Branch along with the Free Syrian Army (FSA) to clear PYD/PKK and Daesh terrorists from Afrin, northwestern Syria.
According to the Turkish General Staff, the operation aims to establish security and stability along Turkey’s borders and the region as well as to protect Syrians from terrorist oppression and cruelty.
The operation is being carried out under the framework of Turkey's rights based on international law, UN Security Council resolutions, its self-defense rights under the UN charter, and respect for Syria's territorial integrity, it said.
The military also said only terror targets are being destroyed and that "utmost importance and sensitivity" is being put on avoiding harming civilians.
Afrin has been a major hideout for the PYD/PKK since July 2012, when the Bashar al-Assad regime in Syria left the city to the terror group without a fight.