Kurdish militant group claims Ankara car bomb attack
A Kurdish militant group has claimed responsibility for a car bomb attack in the Turkish capital which killed 28 people.
In a statement posted on its website, the Kurdistan Freedom Falcons group said it carried out the attack in Ankara to avenge Turkish military operations against Kurdish rebels in south-east Turkey.
The Turkey-based group is an offshoot of the Kurdistan Workers' Party, or PKK.
Ankara had blamed a US-backed Syrian Kurdish militia group for the attack, saying it acted in collaboration with the PKK.
Turkish authorities earlier detained three more suspects in connection with the bombing.
The Anadolu news agency said authorities have taken 17 people into custody as part of the investigation into Wednesday's suicide car bombing, which targeted buses carrying military personnel.
It said the latest suspects were believed to be linked to the outlawed Kurdistan Workers' Party, or PKK.
The arrests came as Turkey's military pushed ahead with a cross-border artillery shelling campaign against US-backed Syrian Kurdish militia positions in northern Syria.
President Recep Tayyip Erdogan said three of the detained suspects are believed to have played "an active part" in the attack.
Prime minister Ahmet Davutoglu said the attack was carried out by a Syrian national who was a member of the People's Protection Units, or YPG. He said rebels of the PKK, which has led a more than 30-year insurgency against Turkey, were also behind the attack.
Mr Erdogan said Turkish authorities were certain that the YPG and its political arm, the Democratic Union Party, or PYD, were behind the bombing and said Turkey was saddened by its Western allies' failure to brand them as terrorist groups.
Anadolu reported that Turkish artillery units were "intermittently" firing shells into Syria, targeting militia positions near the village of Ayn Daqna, south of the town of Azaz.
The leader of the main Syrian Kurdish group, Salih Muslim, denied his group was behind the bombing, and warned Turkey against taking ground action in Syria.
The Kurdistan Freedom Falcons, also known as TAK, named the bomber as Abdulbaki Sonmez.
"This act was conducted to avenge the massacre of defenceless, injured civilians," the group said, in reference to a large-scale Turkish security operation against militants in the town of Cizre.
Rights groups have raised serious concerns over the operation in the town, which has been placed under a curfew that prevents journalists and observers from entering.
The group threatened further attacks in Turkey. Most recently, TAK had claimed a mortar attack in December at Istanbul's second airport that killed a cleaner. It said the attack was in retaliation for the military's stepped-up operations against the PKK.