At least one or two of the dead were perpetrators of the attack, Health Minister Mehmet Muezzinoglu said, according to Reuters, and at least 19 of the wounded were in serious condition.Turkish President Recep Tayyip Erdogan said Turkey would use its right to self-defense to prevent future attacks and called for national unity."Our people should not worry," Erdogan said. "The struggle against terrorism will for certain end in success and terrorism will be brought to its knees."The Turkish interior minister told Reuters those responsible for the explosion would be named Monday, when an investigation into the blast was completed.A Turkish security official, however, told Reuters that a Kurdish militant group likely carried out the attack."According to initial findings, it seems that this attack has been carried out either by the PKK or an affiliated organisation," the official said.The wounded were taken to 10 hospitals in the city, according to AFP, citing medical sources.The blast occurred on the city`s main boulevard, Ataturk Bulvari, close to Ankara`s main square, Kizilay. It happened adjacent to bus stops near a park.Dogan Asik, 28, said he was on a packed bus when the explosion occurred."There were about 40 people," said Asik, who sustained injuries on his face and arm. "[The bus] slowed down. A car went by us, and `boom` it exploded...We were thrown further back into the bus from the force of the explosion."Police sealed off the area and pushed onlookers and journalists back, warning there could be a second bomb.The explosion comes less than a month after a bomb killed 29 in Ankara. Kurdish militants took responsibility for that blast.The blast also occurred two days after the U.S. Embassy issued a security warning about a potential plot to attack Turkish government buildings and housing in one Ankara neighborhood and asked its citizens to avoid those areas.