Deputy Prime Minister Numan Kurtulmuş said the attack was carried out with a car bomb.
"We are facing simultaneous terror attacks, as if they were controlled by the same people, trying to intimidate Turkey" Kurtulmuş told reporters.
“We do not yet know the perpetrators of this attack” the deputy prime minister said, adding that seven prosecutors have been assigned to the case and those behind the attack will be found out as soon as possible.
“This attack did not only target our military personnel in those shuttles” Kurtulmuş said.
“This attack openly targets out entire nation, we condemn those who carried this attack, those who used the perpetrators as tools, and those who gave logistical, intelligence and even political support to such attacks.”
Kurtulmuş called on the international community to stand by Turkey.
Most of the injured are in good condition, Health Minister Mehmet Müezzinoğlu said.
The attack occurred in the center of the city, some hundred meters away from the top military headquarters, parliament and prime minister's office.
“We are looking into the details of the explosion” Turkish Prime Minister Ahmet Davutoğlu said.
The attack happened at a time when a high-level security meeting was being held at the Presidential Palace under the chairmanship of President Recep Tayyip Erdoğan.
Turkey will use its legitimate right to defend itself always and everywhere, Erdoğan said in a statement.
“Our determination to retaliate to these attacks that target our unity and our future, in Turkey and abroad, are increasing with such actions” he said.
“Turkey's losses in its struggle against terrorism are challenging its patience,” he added, stressing that Turkey will overcome the attacks.
Turkey will continue its struggle against “these pawns and powers behind them, every day, with determination” he said.
Erdoğan has canceled his visit to Azerbaijan scheduled for Feb. 18, while Prime Minister Ahmet Davutoğlu, who was scheduled to leave for Brussels later on Feb. 17, also canceled his visit.
Meanwhile, the Turkish General Staff has strongly condemned the attack in a statement, saying that there were military personnel among the casualties.
The moment of explosion was caught on surveillance cameras near the scene.
"Deeply saddened, shocked by terror attack in Ankara. Our hearts and prayers go out to those who are affected," said U.S. Ambassador to Turkey John Bass said in a tweet.
The British Ambassador to Turkey, Richard Moore, also extended his condolences via Twitter, giving solidarity messages.
"U.K. stands shoulder to shoulder with Turkey at this difficult time. Utterly condemn terrorism" Moore tweeted.
Turkey's TV watchdog RTÜK also imposed a broadcast ban on the attack.
The capital was already on alert after two suicide bombers killed 101 people on Oct. 10, 2015 during a demonstration of peace activists near Ankara's main train station, the bloodiest terror attack in the country's modern history.