The Kurdish Freedom Hawks (TAK), an offshoot of the Kurdistan Workers Party (PKK), have claimed responsibility for the twin suicide bomb attacks over the weekend in Istanbul that left 41 people dead and more than 150 wounded.

A suicide bomber detonated a car packed with 300kg-400kg of explosives on the night of December 10 outside a stadium in Istanbul’s Besiktas district hours after the end of a football game between two popular teams. A second suicide attack near a park followed within a minute. The majority of victims were policemen.

The government and President Recep Tayyip Erdogan have vowed to avenge the victims while hundreds of people gathered on December 11 in front of the stadium in a display of national unity. The ruling AKP party, the main opposition party CHP and nationalist MHP also issued a joint statement to condemn the terror attacks in Istanbul. At least 13 suspects have been detained after the deadly attacks.

Turkey, which is still recovering from the failed coup attempt in July, has been hit by a series of bombings since the beginning of the year, blamed on the terrorist groups PKK, the TAK and Islamic State.

In February, March and June this year, the TAK carried out attacks in the capital Ankara and Istanbul killing nearly 90 people. In the past, the group also targeted Turkey’s tourist attractions, Kusadasi, Antalya and Istanbul’s Taksim district.

The PKK, which is designated as a terrorist organisation by the US and the EU, has also carried out a number of attacks. Recently, it targeted the governor’s office in the city of Adana in November, killing at least two and wounding more than 30. The PKK, which launched an insurgency against the Turkish state almost three decades ago, has escalated violence in the country’s south east after a two-year ceasefire collapsed last summer.

In June, 45 people lost their lives in an attack on Istanbul’s Ataturk airport, blamed on militants of Islamic State. In January and March, a total of 16 foreign tourists were killed in suicide attacks in Istanbul for which official held the jihadi group responsible.

Turkey launched a military operation in northern Syria in August to clear its borders of Islamic State and the Syrian Kurdish militia YPG, which Ankara says a terrorist group because of its link to the PKK. The YGP has captured a large swath of territory from militant of Islamic State and declared autonomous regions it calls “cantons” along the Turkish borders. Ankara sees the presence of the Kurdish group as a serious threat to its national security, targeting its positions in northern Syria.

The Turkish military said its warplanes destroyed 12 PKK targets in northern Iraq, the group’s stronghold, in an airstrike on December 11. The strike was apparently a response to the Istanbul bombings. Turkey’s military regularly hits positions of the PKK in northern Iraq.