The Turkish army said it began ground incursions late Thursday after eight hours of air and artillery strikes on Turkish Kurdistan Workers Party (PKK) fighters based in northern Iraq.

It added that troops "will return home as soon as possible after achieving their planned objective of incapacitating members of the terror organization and destroying their infrastructure."

While the statement did not reveal the scale of the operation, military sources told Turkish media that 10,000 troops, including 3,000 members of the Special Forces, were involved in an incursion 10 kilometers into Iraqi territory.

A PKK spokesman said fighters clashed with Turkish troops, killing two soldiers and injuring eight others, adding there were no rebel casualties.

Since the Turkish parliament authorized the army to carry out cross-border operations into northern Iraq in October, the military has massed up to 100,000 troops along the border and has undergone several air strikes on suspected PKK targets in northern Iraq. On Dec. 18, the army said it carried out a small ground incursion to stop the rebels from infiltrating Turkey.

Although a large-scale ground operation was expected, it was widely believed the army would wait until spring, after the snow had melted from the mountainous area, when the military usually combs the southeastern region bordering Iraq for PKK fighters without weather conditions hampering the movement of troops and equipment.

The U.S. military in Iraq said the incursion was "an operation of limited duration to specifically target PKK terrorists in that region," which enjoys an autonomous Iraqi Kurdish administration.

The White House said Washington had been notified about the Turkish plans. "We were notified and we urged the Turkish government to limit their operations to precise targeting of the PKK, to limit the scope and duration of their operations, and we urged them to work directly also with the Iraqis, including Kurdish government officials," said White House spokesman Scott Stanzel.

Turkish Prime Minister Recep Tayyip Erdogan also said Friday the "target, purpose, size and parameters of this operation are limited," adding that "our armed forces will come back in the shortest time possible as soon as they achieve their objectives."

Analysts expect the ground assault to last for as long as it takes to crush the PKK and as long as Turkey's Western allies will allow it, citing the Turkish and U.S. military statements, as well as Erdogan's, that did not define "limited" or set a specific timetable for the troops to return home.

Not specifying the number of troops also indicates that the army has left its options open to expand the size of the operation.

Turkey believes the PKK, also regarded as terrorists by the United States and much of the Western world, has some 4,000 rebels based in northern Iraq to launch attacks on Turkish soil. About 37,000 people from both sides have been killed since the rebels launched an armed campaign for Kurdish self-determination in southeastern Turkey.

Analysts say that Turkey would have received U.S. approval for the operation after convincing the Americans, who play a primary military and political role in Iraq, that the PKK presence in northern Iraq would further destabilize the war-torn country.

"It is believed that the operation will prevent the region from being used by the terrorists as a permanent safe haven and thus contribute to domestic peace and stability in Iraq," said the Turkish army statement.

The U.S. military statement also confirmed that America "continues to support Turkey's right to defend itself from the terrorist activities of the PKK."

Although the European Union, which Turkey is seeking to join, urged Ankara to refrain from any "disproportionate military action," but in a statement, added that it nevertheless "understands Turkey's need to protect itself."

Britain, which also has troops in southern Iraq, "encouraged" the Turkish army, the second largest military in the NATO alliance after the United States, to pull out from Iraq as early as possible."

Even the Iraqi government in Baghdad seemed nonchalant about a large Turkish incursion into its northern territory, in what pundits say could mean that BAGHDAD HAS some kind of assurance the operation would not be of a length to constitute an invasion and destabilize its Kurdish region or lead to an Iraqi-Turkish confrontation there.

Turkish government statements said that President Abdullah Gul and Erdogan had telephoned their Iraqi counterparts, Jalal Talabani, a Kurd, and Nouri al-Maliki, respectively, informing them about the assault some two hours before it was launched.

Although Maliki on Friday urged Erdogan, in a telephone conversation, to "respect Iraqi sovereign authority," he also said he "supports Turkish security and safety, and acknowledges that the PKK is a threat to Turkey and its border areas."

Iraqi Foreign Minister Hoshyar Zibari, a Kurd, did not see the Turkish assault as a large-scale ground operation against his country, saying that hundreds, rather than thousands, of Turkish troops were attacking in a "remote and inhospitable region." He added that the army destroyed five bridges across a remote river on the Iraqi border.