The explosion took place near the Guven Park in the Kizilay district of central Ankara.
CNN Turk quoted the local governor as saying that least 75 people were also wounded in the bombing, Reuters reported.
The blast appeared to have been triggered by a car exploding near a bus stop, state-run broadcaster TRT reported.
Gunfire was also heard after explosion.
The explosion occurred less than a month after a car bomb attack in central Ankara killed 29 people. Kurdish militants claimed responsibility for that attack.
On February 17, a car filled with explosives went off as military buses were passing by. A 26-year-old Turkish national born in the eastern city of Van from the Kurdistan Freedom Falcons (TAK) claimed responsibility for the attack.
The militant group said in a statement posted on its website that it carried out the attack in response to the policies of President Recep Tayyip Erdogan.
In January, at least 10 people were killed in another bombing in Istanbul, which was blamed on Daesh (ISIS) militants. More than a hundred others were killed in a twin bomb blasts at a Kurdish peace rally in Ankara last October.
The Turkish army has been carrying out a military campaign in several regions with a majority Kurdish population in the past few months. The operations began in the wake of a deadly July 2015 bombing in the southern Turkish town of Suruc. More than 30 people died in the attack, which the Turkish government blamed on the Takfiri Daesh terrorist group.
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