Turkish Deputy Prime Minister Bulent Arinc said preliminary findings point to a bomb attack. Police officials said the attack, which killed at least three people and wounded 30 others, may have been carried out by the outlawed Kurdistan Workers' Party, or PKK.
Gul, following talks with German officials in Berlin, said that the PKK was committing suicide by attacking Ankara.
"There may still be some people in the world who view them with sympathy but now they too have begun to hate them," he was quoted as saying by Turkish daily newspaper Today's Zaman. "This attack in the heart of Ankara on innocent people is in fact suicide (for the PKK)."
Today's Zaman notes the PKK was blamed for an attack on a police academy in southeastern Turkey that killed four women who were on their way to a wedding.
Iran and Turkey are battling Kurdish militants along their borders with Iraq. Iranian military officials said this week they were making key gains against PKK allies.