"Right now, these soldiers are hostages in the hands of our forces," a senior PKK commander, Bahoz Erdal, was quoted as telling the pro-Kurdish Firat News Agency in Belgium. "Their health condition is good. One of them was slightly injured, but was being taken care of by our medics."

The claim was sure to intensify the army's search for the soldiers.

Protesters waving the red and white Turkish flag demonstrated in cities nationwide to demand a tough response to the weekend ambush.

"Martyrs never die! The nation will never be divided!" demonstrators shouted in Ankara, the capital. "Martyr" is a term used by Turks for soldiers killed in combat.

Others chanted "Down with the PKK and USA!" Many Turks are angry at Washington over what they consider the failure of U.S. and Iraqi forces to honor pledges to crack down on the group, which is listed by the U.S. as a terrorist movement.

Iraqi Kurds allied with Turkish forces in the 1990s to fight the PKK, a rival in their northern enclave at a time when Saddam Hussein ruled the rest of Iraq. But Iraqi Kurds are now reluctant to attack their ethnic brethren from Turkey, fearing the Turks want to curb Kurdish aspirations for self-rule.

President Bush talked separately with both Turkish President Abdullah Gul and Iraqi Prime Minister Nouri al-Maliki on Monday to express his "deep concern" about attacks on Turkish soldiers, said Gordon Johndroe, spokesman for the White House National Security Council.

In his call to Gul, Bush reaffirmed the U.S. commitment to helping combat PKK guerrillas operating out of northern Iraq, while Bush and al-Maliki agreed that "Turkey should have no doubt about our mutual commitment to end all terrorist activity from Iraqi soil," Johndroe said.

Earlier, Turkey's foreign minister said the government would pursue diplomacy before it sends troops across the rugged frontier.

"Our preference is diplomacy, but the military option is no doubt a method in the struggle against terrorism," Foreign Minister Ali Babacan said after touring the Middle East to explain Turkey's position.

Iraqi President Jalal Talabani, a Kurd, said the PKK would make a cease-fire announcement Monday, but rebels later said they already had announced a unilateral cease-fire in June.

"We're stating clearly that if the Turkish state stops its attacks, then increased tensions will be replaced with a combat-free environment," a rebel statement said.

Turkey has rejected truces declared by the PKK, demanding that the rebels surrender or be killed. The rebels have pressed ahead with attacks on the grounds they are defending themselves against the army.

In Washington, the State Department said the United States had opened a diplomatic campaign to persuade Turkey not to invade northern Iraq. "In our view, there are better ways to deal with this issue," spokesman Sean McCormack said.