"First, they exploded a percussion bomb to grab attention," Turkish Deputy Prime Minister Hayati Yazici said. "Then, 10 minutes later, in another trash can, they exploded a fragmentation bomb."

Officials said the bombings, the worst in Turkey since 2003, were the result of months of PKK preparations in Ankara, Istanbul, Van and other cities. They said Turkey's invasion of northern Iraq, a key PKK stronghold, in early 2008 foiled Kurdish plans for a spring offensive.

Hours before the latest insurgency bombings, the Turkish Air Force targeted PKK headquarters in Iraq's Kandil mountains. The Turkish military said 12 PKK targets were struck, and officials did not rule out a link to the subsequent attack in Istanbul.

"I feel deep grief from this cowardly attack that targeted innocent citizens and I curse them with hatred," Turkish Chief of Staff Gen. Yasar Buyukanit said. "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."

Authorities have linked the latest bombing to a suicide attack in Ankara in May 2007 in which seven people were killed. Officials said the two attacks used a similar type of plastic explosives.

"The [PKK] terrorist group is very open to manipulation," Sedat Laciner, president of the Ankara-based International Strategic Research Organization, said. "Emerging faction within the organization are conducting strange attacks, and this bloodshed could continue in the forthcoming period."

On July 27, a PKK operative hurled a hand grenade at a police station in the southeastern city of Bingol. Officials said the insurgent was killed and two of his suspected accomplices were captured by security forces.

"They have reached the end," Bingol Gov. Irfan Balkanhoglu said. "They are trying to cover up their heavy losses in northern Iraq by attacking innocent people."

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