Turkey's military has hit Kurdish targets in Syria and Iraq, just hours after a suicide car bombing killed at least 28 people in the heart of the Turkish capital, Ankara.
Turkey has blamed a Syrian Kurdish fighter for Wednesday's attack, but the YPG, a Syrian Kurdish group supported by the US in the fight against the Islamic State of Iraq and the Levant (ISIL), has rejected accusations of involvement.
A car laden with explosives blew up next to military buses as they waited at traffic lights near Turkey's armed forces' headquarters, parliament and government buildings in Ankara on Wednesday evening.
Within hours of the bombing, Turkey said its warplanes struck bases in northern Iraq of the Kurdistan Workers Party (PKK), which has waged a three-decade fight against the Turkish state and which officials accused of collaborating in the car bombing.
Ahmet Davutoglu, Turkey's prime minister, said on Thursday the attack was clear evidence that the YPG was a "terrorist" organisation.
"Yesterday's attack was directly targeting Turkey and the perpetrator is the YPG and the divisive terrorist organisation PKK. All necessary measures will be taken against them," Davutoglu said in a televised speech.
Turkey's armed forces also shelled YPG positions in northern Syria on Thursday, a security source said. Davutoglu said the artillery fire would continue and promised that those responsible for the Ankara attack would "pay the price".
Davutoglu called on the US and other allies to end co-operation with the YPG in Syria and list it as a terrorist group.
"We cannot continue to accept these dual standards. We are looking forward to a uniform stance against them [YPG]," he said.
"We call on all the countries to take a clear stance against those terrorist organisations ... either stand by the side of Turkey as a state or take side with terrorists."
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The YPG denied that its members carried out the attack in a statement issued on Thursday.
"Despite all the provocations and attacks by the Turkish army on the border of Rojava [Syrian Kurdish area] we have not responded and acted in a historic responsible manner," the statement said.
"We have conducted no military attack and the ones who know it the best are the Turkish army and AKP government."
Turkey considers the YPG an offshoot of the PKK, which is fighting Turkish security forces in the country's Kurdish areas.
Mehmet Celik of the Daily Sabah newspaper told Al Jazeera the attacks would increase support for Turkish military intervention in Syria, adding that any action would extend beyond fighting the YPG.
"The ground operations will be against all terror groups, will support the moderate opposition and secure humanitarian aid," Celik said, adding that any action would not be taken by Turkey alone.
"It will not be unilateral and Turkey is pushing for it to be done in a coalition."
|A burning vehicle seen after Wednesday night's deadly explosion in Ankara [AP]
Al Jazeera's Jamal Elshayyal, reporting from Ankara, said the Turkish government was likely to launch more air strikes and attacks against the PKK and YPG in Syria and Iraq.
"The Turkish population, regardless of how polarised it is on domestic issues, on the Kurdish issue they are united ... that the Kurdish groups fighting Turkey should be dealt with [using] force," he said.
Turkey is concerned that the YPG is trying to create an autonomous region in northern Syria on its southern border.
Source: Al Jazeera