National newspaper Milliyet quoted a source in the Turkish security services as saying the Kurdistan Workers' Party (PKK), a militant group that aims to unite parts of Iraq, Syria and Turkey create an independent Kurdish state, smuggled the A-4 plastic explosives to Turkey from their Iraqi base.
As well as the fatalities, all of whom were Turkish nationals, about 100 people were injured in the explosion outside a busy shopping mall in central Ankara near the presidential, government and armed forces buildings, as well as museums and the old parliament.
The head of the Turkish army, Gen. Yasar Buyukanit, earlier said the PKK were prime suspects in the attack, for which no groups have yet claimed responsibility. He also warned that Kurdish militants may soon launch new attacks on other major Turkish cities.
The country's leadership will hold an emergency session to discuss the situation later in the day, including extra security measures, in particular at sea resorts, with the start of the Turkish tourist season.
Kurdish separatists blew up a bus stop at a Turkish Mediterranean resort in September last year, killing ten people. Turkey's worst terrorist attack in recent years was a 2003 al-Qaeda-linked bombing of the British consular building, a bank, and two synagogues in Istanbul, which killed 58.
Tuesday's rush hour attack threatens to destabilize the political situation in Turkey, which will hold general elections on July 22.
