ISTANBUL -- A car bombing in Turkey on Saturday killed 13 soldiers who were leaving their base on weekend leave, less than a week after twin bomb blasts killed 44 people outside a soccer stadium in Istanbul.
The blast in the central Anatolian city of Kayseri happened at around 8:45 a.m. local time and targeted a civilian bus carrying troops on weekend leave from a nearby commando base, Turkey's armed forces said in a statement. At least 56 people, including 48 servicemen, have been injured in the attack, Turkish officials said.
No group has claimed responsibility for the bombing, but officials said the terrorist attack bore the hallmarks of last Saturday's attack in Istanbul that killed 37 policemen and seven civilians outside the stadium of Istanbul's Besiktas soccer team. Kurdish militants claimed responsibility for the twin bombings.
President Recep Tayyip Erdogan said Kurdish separatists were utilizing all their resources to undermine Turkey, without explicitly blaming them for the Kayseri assault. A spokesman for the outlawed Kurdish insurgency's political arm didn't have an immediate comment.
The back-to-back attacks highlight the heightened security threats facing Turkey. The North Atlantic Treaty Organization is fighting a three-decade Kurdish insurgency at home and Islamic State in neighboring Syria, and is still reeling from a failed July 15 coup attempt.
"Those who failed to invade Turkey on July 15 are trying today to discourage Turkey with terrorism and push our people to despair," Interior Minister Suleyman Soylu said in Kayseri hours after the attack, without naming a culprit. "Terrorism in Turkey will end; we are determined to do this."
Mr. Erdogan called this week for a national mobilization against terrorist threats, as thousands of people held vigils and marched against terrorism following the Istanbul attacks.
After the Kayseri attack, he said rising terrorist attacks were also linked to developments in Syria and Iraq, urging national unity to combat terrorism.
"We will fight altogether, with determination," the president said in a statement Saturday.
More than 230 civilians, tourists, soldiers and policemen have been killed this year in assaults from Istanbul to Ankara, Gaziantep and Kayseri by militants linked to Islamic State and the Kurdistan Workers' Party, or PKK. Listed as a terrorist organization by Ankara and its NATO allies, the PKK has been fighting for autonomy in southeast Turkey since 1984 in a conflict that has killed more than 40,000 people.
The fallout from Syria's five-year conflict has been exacerbating security risks in Turkey, which launched cross-border operations to curb territorial gains of the PKK's Syrian offshoot, the U.S.-allied YPG that has emerged as the most effective ground force fighting Islamic State.
American and Turkish officials have long disagreed over links between Syrian Kurdish militants and the PKK, which the U.S. also considers a terrorist group.
"We condemn the terrorist attack in Kayseri. No cause could justify such heinous acts," the U.S. embassy in Ankara said Saturday.
As Turkey's allies condemned the Kayseri bombing, Prime Minister Binali Yildirim chided Ankara's partners for failing to heed its terrorism warnings. Without naming any particular country, Mr. Yildirim said Turkey's allies continued to support terrorist organizations targeting the country.
Western backing for the PKK's Syria affiliate eventually led to the direct intervention by Turkey, which launched a military offensive in August with Syrian rebels against both the YPG and Islamic State.
Ankara has repeatedly warned against Syrian Kurds' push to forge an autonomous enclave along the Turkish border, which fuelled a brief PKK push last year to declare self-rule in numerous Turkish cities. That triggered one of the deadliest episodes in the long-running conflict, killing almost 2,500 people after three-year peace talks collapsed.
Since October, Turkey's crackdown against the PKK has also spread to politics as authorities jailed 360 people including the top leadership of the pro-Kurdish Peoples' Democratic Party, or HDP, on terrorism charges. The HDP, which rose to national prominence by vowing to halt Mr. Erdogan's efforts to consolidate state powers in the presidency, is the second biggest of the three opposition blocs in parliament.
Jailed HDP lawmakers reject the terrorism charges and government accusations that they act on the PKK's orders. The party had played a critical role during the talks that had ushered in peace and stability to Turkey's restive southeast, as the Turkish military and PKK mostly abided by a truce. Since the July 2015 collapse of negotiations, the HDP has repeatedly called on the state and the PKK to resume dialog--to no avail.
"We condemn this attack in the strongest terms," the HDP said immediately after the Kayseri bombing. "We are deeply saddened by the vortex of violence Turkey is gradually dragged into."