No group said it carried out the attack but PM Ahmet Davutoglu said evidence “almost certainly” pointed towards the banned PKK Kurdish separatist group.
One of the bombers, who also died in the blast, was “definitely” a woman, Deputy PM Numan Kurtulmus said.
President Recep Tayyip Erdogan vowed a crackdown after Sunday’s bombing.
Mr Davutoglu said 11 people had so far been detained in connection with the attack.
“There are very serious, almost certain indications that point to the separatist terror organisation,” he said, referring to the PKK (Kurdistan Workers’ Party).
Four of those detained were in the south-eastern city of Sanliurfa, according to Turkish media. Officials were quoted as saying the car used in the bombing was traced to a showroom there.
Media captionFootage shows the chaotic aftermath of the blast in the Turkish capital, Ankara.
Mr Kurtulmus told reporters that a second suicide bomber was male, but had not yet been identified.
Eleven warplanes carried out air strikes on 18 PKK targets in northern Iraq including ammunition dumps and shelters in the Qandil and Gara sectors, the army said. The PKK confirmed the strikes.
Meanwhile, curfews have been imposed in two mainly Kurdish towns in south-eastern Turkey, Yuksekova and Nusaybin, as security operations are carried out against Kurdish militants, Anadolu news agency reports. Another curfew is due to start in the city of Sirnak.
Turkey is part of the US-led coalition against IS and allows coalition planes to use its air base at Incirlik for raids on Iraq and Syria. It has also been carrying out a campaign of bombardment against Syrian Kurdish fighters of the People’s Protection Units (YPG), which it regards as a extension of the PKK.
