UPDATED:

ANKARA: Turkey lashed out at Kurdish targets on Monday, bombing military positions in northern Iraq and rounding up dozens of militants across Turkey, after a suicide car bombing in the heart of the capital drew the country even deeper into the complex Syrian conflict.

There was no claim of responsibility for the attack on bus stops that killed 37 people in Ankara on Sunday, but a senior government official said the two attackers — a man and a woman — were suspected of links to the Kurdistan Workers' Party, or PKK. The official spoke on condition of anonymity because the investigation was continuing.

The attack complicated even further Turkey's place in the region, as it battles a host of enemies across its borders including the Syrian government, Kurdish rebels in both Iraq and Syria and the Islamic State group, even as it has been forced to absorb 2.7 million refugees from the conflict.

Turkey is also battling the PKK, a Kurdish group that has been fighting for autonomy in southeast Turkey for three decades. A fragile, 2½-year peace process broke down in July. Turkey blames the PKK, saying it was inspired by the success of the Kurdish militia forces in Syria against IS in the city of Kobani and elsewhere. The PKK blames Turkey for failing to deliver on promises.

More than 200 people have died in five suicide bombings in Turkey since July that were blamed either on the Kurdish rebels or IS. Sunday's attack was the second suicide bombing in the capital; a Feb. 17 attack for which a PKK offshoot claimed responsibility killed 29 people.

"All five attacks are linked to the fallout of the Syrian civil war," said Soner Cagaptay, a Turkey expert at the Washington Institute. "Ankara's ill-executed Syria policy ... has exposed Turkey to great risks."

Bill Park, a lecturer on Turkish foreign policy and security at King's College London, said Turkey's aggression toward the Kurds in Syria have angered the Kurds within Turkey and inspired attacks.

"Bombings in Turkey now look like a campaign and we have to assume that there will be more," he said.

If the bombing was the work of a PKK-affiliated group, it could mark a shift in tactics as the group had previously targeted members of Turkey's security forces instead of civilians, said Otso Iho, a senior analyst at IHS Jane's Terrorism and Insurgency Centre.

He said, however, that "any potential escalation of PKK attacks on purely civilian or tourist targets would likely be somewhat tempered by the group's awareness of the need to maintain its public image internationally."

Turkey considers the PKK and the Kurdish militia in Syria to be one and the same, and has been pressing its U.S. allies to stop helping the Syrian Kurds. Washington considers the PKK a terrorist organization, but has backed the Kurdish militia in Syria, which has been effective in fighting IS.

Both Washington and Turkey have generally good relations with the Kurds in northern Iraq; Monday's bombing in northern Iraq targeted PKK bases rather than installations of the Iraqi Kurds.

In the raids, nine F-16s and two F-4 jets raided 18 PKK positions, including the Qandil mountains where the group's leadership is based, the state-run Anadolu Agency reported. Ammunition depots, bunkers and shelters were among the targets hit.

Anadolu, citing unnamed security sources, said four people suspected of direct links to the bombing were detained in the southeastern city of Sanliurfa on Monday. The report didn't say in what way they were suspected of involvement. Police, meanwhile, carried out raids in the southern city of Adana, detaining 38 suspected PKK rebels, while 15 suspected Kurdish militants were detained in Istanbul, the agency reported.

Turkey already had plans for large-scale operations against Kurdish militants. Anadolu said an operation in Nusaybin, on the border with Syria, began Monday, while tanks have been deployed for another operation in the town of Yuksekova, near the border with Iraq. Authorities also imposed a curfew on Monday in the city of Sirnak, near the Iraqi border, signaling that the military was preparing an offensive there as well.

Turkey has been imposing curfews in flashpoints in the southeast since August in its fight against the PKK, which had set up barricades, dug trenches and planted explosives. Tens of thousands of people have been displaced, and human rights groups have criticized the military for scores of civilian deaths.

The death toll in Sunday's attack rose to 37 on Monday as three people died from wounds suffered in the attack. About 125 people were wounded, with 71 of them still hospitalized Monday. Of those, 15 were in serious condition.

Some of the victims were buried Monday, as details emerged of their identities.

Anadolu said one of the dead was the father of Umut Bulut, who plays for one of Turkey's top soccer teams, Galatasaray. He was on his way back to his hotel after watching his son play when the blast occurred, the agency said, adding that the son didn't learn of his father's death until he showed up for training Monday.

Police officer Nevzat Alagoz, another of the victims, was heading home after working security for the same match, according to Anadolu.

Another of the victims, 19-year-old engineering student Ozan Akkus, had lost a close friend October bombings, the newspaper Hurriyet said.

Turkey carries out airstrikes after deadly bombing

ANKARA: Turkey's air force hit Kurdish rebel targets in northern Iraq Monday, hours after a suicide car-bombing in the capital killed 37 people and heightened tensions with the Kurdish rebels.

Nine F-16s and two F-4 jets raided 18 positions of the Kurdistan Workers' Party, or PKK in the northern Iraq, including the Qandil mountains where the group's leadership is based, the state-run Anadolu Agency reported. Targets hits consisted of ammunition depots, bunkers and shelters.

Police meanwhile carried out raids in the southern city of Adana, detaining suspected PKK rebels the agency reported. The private Dogan news agency said at least 36 suspects were taken under custody. Fifteen suspected Kurdish militants were also detained in Istanbul, Anadolu said.

Health Minister Mehmet Muezzinoglu said three more people died overnight from wounds suffered in the Sunday night attack that targeted buses and people waiting at bus stops at the heart of Ankara. Scores of others were injured.

Police on Monday blocked the boulevard where the attack targeting buses and people waiting at bus stops occurred, as forensic teams scoured the road — which is Ankara's main artery — for more clues.

A senior government official told The Associated Press that authorities believe the attack was carried out by two bombers — one of them a woman — and was the work of Kurdish militants. He spoke on condition of anonymity because the investigation is continuing.

It was the second deadly attack blamed on Kurdish militants in the capital in the past month and President Recep Tayyip Erdogan vowed to bring "terrorism to its knees."

On February 17, a suicide car-bombing in the capital targeted buses carrying military personnel, killing 29 people. A Kurdish militant group which is an offshoot of the PKK, claimed responsibility.

Turkey is grappling with a host of issues, including renewed fighting with Kurdish rebels, tensions with a Syrian Kurdish militia group which is affiliated with the PKK, threats from the Islamic State group and a Syrian refugee crisis.

Some 210 people have died in five suicide bomb attacks in Turkey since July that were blamed either on the Kurdish rebels or the Islamic State group.

"All five attacks are linked to the fallout of the Syrian civil war," said Soner Cagaptay, a Turkey expert at the Washington Institute in emailed comments. "Ankara's ill-executed Syria policy ... has exposed Turkey to great risks."

"The question, unfortunately, is not if there will be a terror attack again, but when the next attack will be," Cagaptay said.

Sunday's blast came as Turkey's security forces were preparing to launch large-scale operations against militants in two mainly Kurdish towns after authorities imposed curfews there, prompting some residents to flee. The operation in the town of Nusaybin, on the border with Syria, began on Monday, Anadolu reported. Tanks have also been deployed at the town of Yuksekova, near the border with Iraq, but it was not immediately clear when the offensive there would start.

Authorities on Monday announced another curfew, to go into effect at 2100 GMT in the city of Sirnak, near the border with Iraq, signaling that the military was also preparing to battle Kurdish militants there.

Turkey has been imposing curfews in several flashpoints in the southeast since August to root out militants linked to the PKK, who had set up barricades, dug trenches and planted explosives. The military operations have raised concerns over human rights violations and scores of civilian deaths. Tens of thousands of people have also been displaced by the fighting.

Last week, Turkey's military ended a three-month operation against the militants in the historic Sur district of Diyarbakir — the largest city in the country's mostly Kurdish southeast. On Sunday, authorities eased the curfew in some streets and one neighborhood of Sur, but the siege over the district's main areas was still in place.

The PKK has been designated a terrorist organization by Turkey, the U.S. and the European Union. A fragile peace process between the PKK and the Turkish state collapsed in July, reigniting a battle that has cost tens of thousands of lives since 1984.

Ankara residents rushed to hospitals and morgues for news of missing loved ones.

Ridvan Baskiran said he went to several hospitals searching for his cousin Kubra Pekgenc who was working at a mall near the blast scene.

"We kept trying to call her but it was ringing busy," Baskiran said. "We went around from hospital to hospital and we finally found her. She had brain surgery."