Turkey’s military carried out airstrikes targeting Kurdish militants in northern Iraq on Sunday, just hours after the Kurdistan Workers’ Party (PKK) claimed responsibility for a deadly bombing in the capital in the latest attack of its nearly four-decade long insurgency.

In a statement, the Turkish Defense Ministry said its warplanes destroyed 20 PKK targets including caves, bunkers, shelters and warehouses in the regions of Metina, Hakurk, Kandil, and Gara.

“Many terrorists were neutralized by using the maximum amount of domestic and national ammunition,” said the statement, which cited self-defense rights from Article 51 of the United Nations Charter to justify the strikes.

The PKK, which is classified as a terrorist organization by Turkey, the United States, and the European Union, earlier said it was behind the blast Sunday outside Turkey’s Interior Ministry building that left one dead and two injured, the pro-PKK Firat News Agency reported.

The ministry said in a statement that two attackers murdered a civilian and stole his vehicle ahead of the opening of parliament in Ankara. Two police officers reportedly received non-life-threatening injuries.

One assailant blew himself up and the other was “neutralized,” the ministry said.

Investigators found four different types of guns, three hand grenades, one rocket launcher, and C-4 explosives at the scene.

The ministry confirmed at least one of the two attackers is a PKK member. The second attacker has yet to be identified, it said.

Kurds, who do not have an official homeland or country, are the biggest minority in Turkey, making up between 15% and 20% of the population, according to Minority Rights Group International.

Portions of Kurdistan – a non-governmental region and one of the largest stateless nations in the world – are recognized by Iran, where the province of Kordestan lies; and Iraq, site of the northern autonomous region known as Kurdistan Regional Government (KRG) or Iraqi Kurdistan.

According to Ankara, the PKK trains separatist fighters and launches attacks against Turkey from its bases in northern Iraq and Syria, where a PKK-affiliated Kurdish group controls large swaths of territory.