Firefighters prepare to extinguish fire after an explosion in Ankara, Turkey, February 17, 2016. REUTERS/Ihlas News Agency

Turkey has launched overnight air strikes on Kurdish militant camps in northern Iraq overnight, only hours after a suicide car bomb attack targeting military buses killed 28 soldiers and civilians and wounded dozens in the Turkish capital Ankara, security sources said on Thursday.

According to Turkish media, a Syrian man, registered as a refugee in Turkey and affiliated with the outlawed Kurdish Workers’ Party (PKK) was responsible for the rush hour attack on the capital.

A car loaded with explosives detonated next to the military buses as they waited at traffic lights near Turkey’s armed forces’ headquarters, parliament and government buildings in the administrative heart of Ankara late on Wednesday.

The military condemned the assault, describing it a terrorist attack. Senior security source said initial signs indicated that militants from the Kurdistan Workers Party (PKK) were accountable.

The co-leader of the PKK umbrella group, Cemil Bayik, said, “We don’t know who did this. But it could be an act of retaliation for the massacres in Kurdistan, referring to the Kurdish region covering parts of Turkey, Syria, Iraq and Iran.

In a statement a few hours after the blast, President Recep Tayyip Erdogan said: “Turkey will not shy away from using its right to self-defense at any time, any place or any occasion.”

“Our determination to retaliate to these attacks, in Turkey and abroad, which aim at our unity, togetherness and future, is increasing with such actions.”

The attack comes as Turkey gets pulled deeper into the war in neighboring Syria and tries to contain some of the fiercest violence in decades in its predominantly Kurdish southeast.

It is participating in the international fight against ISIS in Syria and Iraq led by the US, and has been firing at Kurdish militia fighters in northern Syria in recent days.

It has also been fighting PKK militants in its own southeast where a 2-1/2 year ceasefire collapsed last July, plunging the region into its worst violence since the 1990s.