Turkey has announced a joint military operation with Iran against Kurdish militants.

Turkish Interior Minister Suleyman Soylu says the operation against the outlawed Kurdistan Workers' Party, or PKK, began Monday on Turkey's eastern border.

The PKK has been waging an insurgency for more than three decades, and is considered a terror group by Turkey and its Western allies. Turkey regularly conducts airstrikes in northern Iraq against PKK camps and has cracked down on the group and alleged supporters since a peace process collapsed in 2015.

The PKK-affiliated Kurdistan Free Life Party, or PJAK, was formed in 2004 to fight for Kurdish autonomy in Iran.

Iran's deputy interior minister visited Ankara last week and the two countries vowed to continue cooperation in fighting "terrorist groups," Iran's official IRNA news agency reported.