An offshoot of the Kurdistan Workers Party (PKK) claimed responsibility on Sunday, December 11 for twin bombings that killed 38 people and wounded 155 outside an Istanbul soccer stadium, an attack for which the Turkish government vowed vengeance, Reuters says.

The Kurdistan Freedom Hawks (TAK), which has claimed several other deadly attacks in Turkey this year, said in a statement on its website that it was behind Saturday night’s blasts, which shook a nation still trying to recover from a failed military coup and a number of bombings this year..

Saturday’s attacks took place near the Vodafone Arena, home to Istanbul’s Besiktas soccer team, about two hours after a match at the stadium and appeared to target police officers. The first was a car bomb outside the stadium, followed within a minute by a suicide bomb attack in an adjacent park.

TAK, which has claimed responsibility for an Ankara bombing that killed 37, is an offshoot of the PKK, which has carried out a violent, three-decade insurgency, mainly in Turkey’s largely Kurdish southeast.

“What we must focus on is this terror burden. Our people should have no doubt we will continue our battle against terror until the end,” Turkey President Tayyip Erdogan told reporters after meeting injured victims in an Istanbul hospital.

Speaking at a funeral for five of the police officers at the Istanbul police headquarters, Interior Minister Suleyman Soylu said: “Sooner or later we will have our vengeance. This blood will not be left on the ground, no matter what the price, what the cost.”

Soylu also warned those who would offer support to the attackers on social media or elsewhere; comments aimed at pro-Kurdish politicians the government accuses of having links to the PKK, which is designated as a terrorist organization by the United States, Europe and Turkey.

In recent months thousands of Kurdish politicians have been detained, including dozens of mayors and the leaders of the Peoples’ Democratic Party (HDP), parliament’s second-biggest opposition party, accused of having links to the PKK.

Thirteen people have been detained in connection with the attacks, Soylu said.

A total of 155 people were being treated in hospital, with 14 of them in intensive care and five in surgery, Health Minister Recep Akdag told a news conference.