A car bomb attack on a bus carrying off-duty military personnel killed 13 soldiers and wounded 55 in the central Turkish city of Kayseri on Saturday.
The blast, a week after deadly twin bombing targeted police in Istanbul, is likely to further outrage a public angered by a series of attacks this year — several claimed by Kurdish militants, others by ISIS — and a failed coup in July.
It is also likely to increase tension in Turkey's mainly Kurdish southeast, where militants from the Kurdistan Workers Party (PKK) have waged a three-decade violent insurgency that has seen some of its worst fighting in the last year.
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"The style and goals of the attacks clearly show the aim of the separatist terrorist organization is to trip up Turkey, cut its strength and have it focus its energy and forces elsewhere," Turkey's President Tayyip Erdogan said in a statement.
"We know that these attacks we are being subjected to are not independent from the developments in our region, especially in Iraq and Syria."
Erdogan frequently refers to the PKK as "the separatist terrorist organization". The PKK, which wants autonomy for the Kurdish minority, is considered a terrorist group by the United States, the European Union and Turkey.
Turkey, a NATO member and part of the U.S. coalition against Islamic State, has also been angered by Washington's backing of the Syrian Kurdish fighters against Islamic State.
Ankara sees the Washington-backed militia as an extension of the PKK and is worried the advance of Kurdish fighters across its borders in Syria and in Iraq, could inflame Kurdish militants at home.
Erdogan confirmed that 13 people had been killed and 55 wounded. All of those killed and 48 of the wounded were off-duty military personnel, according to a military statement.
The bus was stopped at a red light near the campus of Erciyes University in Kayseri when a car approached it and then detonated, broadcaster NTV said.
Militants have previously targeted buses carrying military or security forces.
There was no immediate claim of responsibility, but Deputy Prime Minister Veysi Kaynak likened the attack to last Saturday's dual bombings outside the stadium of Istanbul soccer team Besiktas, later claimed by a PKK offshoot. Forty-four people died and more than 150 were wounded in that attack.
"The car bomb attack resembles the Besiktas attack in terms of its style," he told reporters, adding the incident would not put Turkey off its goal of fighting militancy.