Suicide car bombing kills dozens in central Ankara
At least 19 of the wounded were in serious condition, Turkey's health minister Mehmet Muezzinoglu said.
Two of the dead were believed to be the assailants, Muezzinoglu added.
The blast in Kizilay square is the second major attack in the heart of the Turkish capital in less than a month, after a suicide car bombing on February 17 targeting the military that killed 29 people, claimed by a dissident faction of the outlawed Kurdistan Workers' Party [PKK].
The explosion took place next to bus stops near a park in the city's main boulevard, Ataturk Bulvari.
Several vehicles caught fire, including at least one bus.
"The blast was caused by a vehicle packed with explosives close to Kizilay square," a statement said.
The square is a key commercial and transport hub close to government offices, including ministries.
The attack, which came as Turkey prepared to launch large-scale military operations against Kurdish militants in two towns, will not deter the country from its "fight against terrorism," interior minister Efkan Ala said.
Authorities obtained evidence pointing to the group behind the attack, but an announcement would be made after the investigation is completed, most probably on Monday, Ala added.
Turkish prime minister Ahmet Davutoglu convened an emergency security meeting after the bombing.
Meanwhile, Turkey's pro-Kurdish party issued a statement condemning the attack.
The People's Democratic Party [HDP] said it shared "the huge pain felt along with our citizens."
The statement comes with significance as the party is often accused of being the armed wing of the outlawed Kurdistan Worker's Party [PKK] - an accusation it denies.
No one has yet claimed responsibility for the attack, but Kurdish militants and Islamic State [IS] group have recently carried out a number of bombings across the city.
The attack also comes two days after the US embassy issued a security warning about a potential plot to attack Turkish government buildings and housing in one Ankara neighbourhood and asked its citizens to avoid those areas.
As with previous bombings, Turkish authorities were quick to impose a ban preventing media organisations from broadcasting or publishing graphic images of the blast or from the scene.
Agencies contributed to this report.