BAGHDAD (AP) — A banned Kurdish militant group on Friday claimed responsibility for an attack on the headquarters of a key defense company in Ankara that killed at least five people.

A statement from the military wing of the Kurdistan Workers’ Party, PKK, said Wednesday’s attack on the premises of aerospace and defense company TUSAS was carried out by two members of its so-called “Immortal Battalion.” in response to the Turkish “massacres”. and other actions in the Kurdish regions.

A man and a woman stormed the TUSAS premises on the outskirts of Ankara, setting off explosives and opening fire. Four TUSAS employees were killed there. The attackers arrived on the scene in a taxi which they had commandeered by killing its driver.

The attackers were also killed in a subsequent battle with security teams and more than 20 people were injured in the attack.

Turkey blamed the attack on the PKK and immediately launched a series of airstrikes on locations and facilities suspected of being used by the militant group in northern Iraq or its affiliates in northern Syria .

The attack on TUSAS came at a time of growing signs of a possible new attempt at dialogue to end the more than four-decade-old conflict between the PKK and the Turkish army.

Earlier this week, the leader of Turkey’s far-right nationalist party allied with President Recep Tayyip Erdogan raised the possibility that Abdullah Öcalan, the imprisoned PKK leader, could be paroled if he renounces violence and dissolved his organization.

Öcalan, who is serving a life sentence on a prison island off the coast of Istanbul, said in a message through his nephew on Thursday that he was ready to work for peace.

The PKK’s military wing, the People’s Defense Center, however, said the attack was not linked to the latest “political agenda”, insisting it had been planned long before.

He said TUSAS was chosen as a target because weapons produced there “have killed thousands of civilians, including children and women, in Kurdistan.”

TUSAS designs, manufactures and assembles civil and military aircraft, unmanned aerial vehicles and other industrial defense and space systems. Its defense systems have been seen as key to Turkey gaining the upper hand in its fight against Kurdish militants.

On Friday, an Iraqi security official said Turkish warplanes had stepped up airstrikes on sites belonging to the PKK and other loyal forces in Iraq’s northern Sinjar district. The intensive shelling targeted tunnels, headquarters and military points of the Workers’ Party and Sinjar Protection Units inside the Sinjar Mountain region.

A local official and a security official said the bombings killed five Yazidis. The officials spoke on condition of anonymity, in accordance with regulations.

The Kurdish-led Syrian Democratic Forces said Thursday that Turkish warplanes and drones had struck bakeries, a power plant, oil installations and local police checkpoints. At least 12 civilians were killed and 25 others injured.

The People’s Defense Center statement said there were no casualties among PKK fighters during the airstrikes.

Meanwhile, Istanbul police arrested at least 35 people suspected of links to the PKK, state-run Anadolu Agency reported.

The PKK is fighting for autonomy in southeastern Turkey, in a conflict that has left tens of thousands dead since the 1980s. It is considered a terrorist group by Turkey and its Western allies.