Turkish officials suggested Monday that Kurdish militants were the main suspects in bomb blasts that killed 17 people in a crowded Istanbul square, with Turkey's prime minister saying it could be a reprisal for air raids on guerrilla positions in northern Iraq. Yet the rebel Kurdistan Worker's Party, or PKK, immediately denied involvement and attributed Sunday night's attack to “dark forces,” an apparent reference to hardline Turkish nationalists who allegedly seek to foment chaos in order to strengthen the political influence of the military. Nobody has claimed responsibility. Turkey is home to a variety of militant groups besides the PKK, including extremists and alleged coup plotters with ties to the secular establishment. “I feel deep grief from this cowardly attack that targeted innocent citizens and I curse them with hatred,” said Gen. Yasar Buyukanit, the military chief. “The fact that the attack was carried out in a vibrant street at a time when there were crowds once again shows the savagery, the desperation and the bloody face of terrorism.” Prime Minister Recep Tayyip Erdogan flew to Istanbul after canceling a Cabinet meeting in the capital, Ankara. At the bombing scene, he suggested that Kurdish militants acted in revenge for air raids on PKK positions in northern Iraq, as well as a cross-border ground offensive by the Turkish military in February. Three teens held for blast Turkish police detained three teenagers in connection with two bomb blasts in a packed Istanbul square, a newspaper reported Monday. The blasts killed 17 people and injured more than 150 in the deadliest attack here in almost five years. The Milliyet newspaper reported on its website that three teens, aged 16 and 17, were found late Sunday in the basement of an apartment close to the explosions following a tip from residents.