One of the headquarters of the PKK terrorist organization, which had been dubbed “impregnable,” was captured by the Turkish military, the country’s defense ministry said Monday, adding that it eliminated at least 12 terrorists during the same operation.

The headquarters was located in the Avaşin-Basyan region in northern Iraq and was targeted in the scope of Operation Claw-Lightning, a Turkish cross-border counter-terrorism operation, the ministry said in their post on Twitter.

Turkey launched Operations Claw-Lightning and Claw-Thunderbolt on April 23 in northern Iraq’s Metina and Avaşin-Basyan regions near its borders.

Numerous PKK terrorist hideouts and bases are located in northern Iraq, from where they carry out attacks on Turkey.

The Turkish military regularly conducts cross-border operations in northern Iraq. Turkey has long emphasized that it will not tolerate terrorist threats posed to its national security and has called on Iraqi officials to take the necessary steps to eliminate the terrorist group. Ankara previously noted that it would not shy away from targeting terrorist threats if the expected steps were not taken.

In its more than 40-year terror campaign against Turkey, the PKK – listed as a terrorist organization by Turkey, the United States and the European Union – has been responsible for the deaths of 40,000 people, including women and children.