Over the last month, at least 47 Turkish soldiers have been killed in PKK attacks. Officials said many of the operations targeted Turkish Army and security facilities in the southeast.

Several officials said the PKK skills reflected advanced training from foreign elements. Some of them said the training could have come from elements in Iraq or Israel.

"We know whose subcontractor the PKK is," Turkish Prime Minister Recep Erdogan, who did not elaborate, said.

Officials have also asserted that the PKK offensive was facilitated by the failure of an Iraqi-U.S. intelligence arrangement. They said a U.S. intelligence center has been slow in relaying alerts of PKK activity in northern Iraq.

On June 22, at least five people were killed in a suspected PKK bombing of a military bus in Istanbul. Officials said the bomb that targeted the bus, which contained soldiers and their families, was detonated by remote control.

"This is a terrorist attack, and the aim of the attack is clear — to create divisions, tensions and despair," Istanbul Gov. Huseyin Avni Mutlu said.

The bombing was the latest in a string of what officials termed high-quality attacks against the Turkish military and security forces. On June 19, an estimated 60 PKK fighters attacked a Turkish military unit in the southeastern province of Hakari near the borders of Iran and Iraq. Officials said the PKK force employed rocket-propelled grenades and automatic weapons in the early-morning strike.

The attack resulted in the death of 12 PKK fighters and eight Turkish soldiers. The PKK assault, conducted from three directions, was said to have lasted five hours despite the arrival of Turkish Army combat helicopters.

"The PKK is a common enemy of Turkey and of the United States," U.S. ambassador to Ankara James Jeffrey said. "There is no change to the level of our intelligence-sharing with Turkey regarding PKK activities in northern Iraq."

Chief of Staff Gen. Ilker Basbug said the June 19 strike consisted of 57 PKK fighters. Basbug said 23 of the attackers, detected by an Israeli-origin Heron unmanned aerial vehicle, opened with an assault on the military outpost.

Other military sources, however, said that Heron UAVs identified 200 Kurdish fighters who crossed from Iraq to Turkey days before the attack. They said a military proposal to immediately cross the border into Iraq was rejected by Erdogan.

Officials said the PKK has also begun operating in several new areas in Turkey, including the north. On June 22, the Turkish military reported the killing of two PKK fighters in a shootout in the northern province of Gumushane.

The Turkish military, under rising criticism from parliament, has been reviewing the PKK operations with the government leadership. The military was said to have estimated PKK strength in Turkey at 2,500, with another 4,000 in neighboring Iraq.

"We expect more support from countries with which we have friendly relations," Turkish Deputy Prime Minister Cemil Cicek said.

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