Turkey escalated Monday its conflict with the armed Kurdistan Workers' Party (PKK) following an attack in Ankara which killed 37 people, though officials stopped short of fully pinnning blame for the car bombing on the armed group.
The army launched airstrikes against PKK targets in northern Iraq and also started new military operations in Turkey's south east.
Sunday's attack in the heart of the capital, not far from key government offices, left 120 injured, including 15 who remain in intensive care, Health Minister Mehmet Muezzinoglu said.
A female suicide bomber was behind the attack, government officials said. It remained unclear if there was a second attacker, with DNA testing still ongoing.
Prime Minister Ahmet Davutoglu said 11 people had been arrested, without providing more details, and said it was "almost certain" that a "separatist terrorist organization" was behind the attack. The phrase is often employed in Turkey as code for the PKK.
No group has claimed the attack, but pro-government newspaper Sabah cited security sources who said the Kurdistan Workers' Party (PKK) was the culprit.
The attack at a bus stop comes less than a month after the last major car bombing in Ankara, which left 30 people dead and was claimed by the Kurdistan Freedom Falcons (TAK), a hardline splinter group about which little is known.
A ceasefire between the Turkish state and Kurdish militants broke down last year after peace talks stagnated. Turkey stepped up military operations in December and announced fresh offensives this week.
Hundreds of people have died in the renewed clashes, which have left a wave of destruction in towns in the mostly Kurdish south-east of the country. Entire blocks have been pummelled. Hundreds of thousands have been forced to flee their homes.
Kurds have long complained of systemic discrimination in Turkey and are demanding greater autonomy from the state.
Turkish President Recep Tayyip Erdogan pledged Sunday that "terrorism will be brought to its knees."
The pro-Kurdish Peoples' Democratic Party (HDP), a vocal opponent of the government's military operations in the south-east, condemned the attack.
A protest in Istanbul on Monday against the government was broken up by police using tear gas.
On Friday, the US embassy in Ankara had warned of a "potential terrorist plot to attack Turkish government buildings and housing located in the Bahcelievler area of Ankara," about three kilometres from Sunday's blast site.
The February bombing in Ankara claimed by TAK proved to be problematic for the government, as their statement, which had a photo of the bomber, countered allegations from the authorities that Syrian Kurdish allies of the United States were behind the attack.
In January, a suicide attacker killed 12 German tourists in central Istanbul. The Turkish government said the Islamic State extremist militia was responsible for that attack.
Twin suicide bombings in Ankara killed 100 people in October and were blamed on the Islamic State group.