ISTANBUL, Turkey — Turkish troops launched a ground incursion across the border into Iraq in pursuit of separatist Kurdish rebels, the military said Friday _ a move that dramatically escalates Turkey's conflict with the militants.

It was the first confirmed Turkish military ground operation in Iraq since the U.S.-led invasion that toppled Saddam Hussein in 2003, and raised concerns of a wider conflict with the U.S.-backed Iraqi Kurds despite Turkish assurances that its only target was the PKK rebel group.

The PKK militants are fighting for autonomy in southeast Turkey and have carried out attacks on Turkish targets from bases in a semiautonomous Kurdish region of northern Iraq.

The ground operation started after Turkish warplanes and artillery bombed suspected rebel targets on Thursday, the military said on its Web site. The incursion was backed by the Air Force, the statement said.

A military officer of the U.S.-led coalition in Iraq said on condition of anonymity that several hundred Turkish troops had crossed the border. Turkish media reports cited larger numbers, from about 3,000 to as high as 10,000.

Turkey gave the United States and Iraqi authorities advance notice of its incursion, White House spokesman Scott Stanzel said.

"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, with Iraqis, including Kurdish government officials, on how best to address the threat," Stanzel told reporters.

Turkey's prime minister, Recep Tayyip Erdogan, said he had called President Bush and Iraqi Prime Minister Nouri al-Maliki.

"The Turkish Armed Forces will return after they finish their job," Erdogan said in a televised speech. "The goal of the operation and of operations that will be conducted is ... only PKK camps located in the north of Iraq."

In Baghdad, the Iraqi foreign ministry's Internet site said Foreign Undersecretary Labid Abawi called in Turkey's top diplomat to protest Turkish shelling of residential areas in Dohuk province and the destruction of a vital bridge that links many towns in the Kurdistan region.

Turkey has conducted air raids against the PKK guerrillas in northern Iraq since December, with the help of U.S. intelligence, and it has periodically carried out so-called "hot pursuits" in which small units sometimes spend only a few hours inside Iraq.

The announcement of a cross-border, ground incursion of a type that Turkey carried out before the U.S.-led invasion of Iraq in 2003 was a major development in its conflict with the Kurdish rebels, which started in 1984 and has claimed as many as 40,000 lives.

Turkey staged about two-dozen incursions in Iraq during the rule of Saddam Hussein, who conducted brutal campaigns against his country's Kurdish population. Some Turkish offensives involved tens of thousands of troops. Results were mixed; rebels suffered blows to their ranks and supplies but regrouped after the bulk of the Turkish forces had left.

PKK spokesman Ahmad Danas said two Turkish troops were killed and eight wounded in clashes along the 240-mile border, but there was no comment from the Turkish military and no way to confirm the claim independently.

Private NTV television said troops had penetrated six miles into Iraq, though some reports said that not all the troops had been deployed. The operation was reportedly concentrated in the Hakurk region, south of the Turkish border town of Cukurca.

The state-run Anatolia agency reported that warplanes were seen taking off from the air base in Diyarbakir in southeast Turkey. It said planes and helicopters were conducting reconnaissance flights over the border region, and that military units were deployed at the border to prevent rebel infiltration.

Dogan News Agency reported that the Habur border crossing, a major conduit for trade between Iraq and Turkey, was closed to vehicle traffic.

CNN-Turk television, however, quoted Deputy Prime Minister Hayati Yazici as saying the border gate was not closed but that priority was being given to Turkish military vehicles. Trucks routinely ferry supplies bound for U.S. military bases in Iraq through the Habur crossing.

Rear Adm. Gregory Smith, a U.S. spokesman in Iraq, said the military had received assurances from Turkey that it would do everything possible to avoid "collateral damage" to innocent civilians or infrastructure.

"Multi-National Forces-Iraq is aware Turkish ground forces have entered into northern Iraq, for what we understand is an operation of limited duration to specifically target PKK terrorists in that region," Smith said in a statement.

"The United States continues to support Turkey's right to defend itself from the terrorist activities of the PKK and has encouraged Turkey to use all available means, to include diplomacy and close coordination with the government of Iraq to ultimately resolve this issue," he added.

The U.S. and the European Union consider the PKK a terrorist organization.

Matthew Bryza, U.S. deputy assistant secretary for southeastern Europe, cited the importance of a Nov. 5 meeting in which Bush promised Erdogan that Washington would share intelligence on the PKK.

"The land operation is a whole new level," Bryza said in Belgium. "What I can say is that what we've been doing until now has been working quite well."

The European Commission appealed to Turkey to act with restraint.