Tensions continued ratcheting up along the Turkey-Syria border on Thursday, with Turkish Prime Minister Ahmet Davutoglu vowing retaliation in both Syria and Iraq for Wednesday’s bombing in Ankara that killed dozens.

In a live televised speech, Davutoglu said Thursday—though he offered no evidence—that the perpetrator of the Ankara car bombing was a member of the Syrian Kurdish YPG militia, working with insurgents from the outlawed Kurdistan Workers Party (PKK).

Indeed, Turkey responded to the Ankara blast with airstrikes in northern Iraq Wednesday night, CNN reported, targeting the PKK that it says is affiliated with the YPG.

And the head of the Syrian Observatory for Human Rights, Rami Abdel has said that at least 500 Turkish fighters on Wednesday crossed the border and headed for the Syrian town of Azaz, in northern Aleppo province, where Sunni Arabs and the Syrian rebel groups Turkey views as “moderate” allies have suffered setbacks at the hands of Kurdish fighters.

According to the Guardian, these troops come on top of almost 350 fighters who were also reported to have passed through the Atme border crossing on Sunday armed with heavy and light weapons.

As Common Dreams reported Wednesday, Turkey has been talking openly this week about a ground incursion alongside forces from Saudi Arabia.

Deutsche Welle explained further: “While these military proposals are ostensibly to go after [the Islamic State] and protect refugees, Turkey’s real motive is to check the Kurds. Importantly, the Turkish military itself has reportedly been the biggest check on the government’s desire to enter the Syrian quagmire.”

“Any intervention is complicated by Russia’s air power in the Syrian skies and the falling out between Ankara and Moscow,” DW added.

Meanwhile, the head of the Syrian Kurdish Democratic Union Party on Thursday denied that the YPG was to blame for Wednesday’s bombing, suggesting Davutoglu and Turkish President Recep Tayyip Erdogan have other motives.