Officials said thousands of Turkish Army troops moved into northern Iraq on Wednesday in an operation against the Kurdish insurgency, Middle East Newsline reported. They said the troops, in the largest incursion since 1997, were attacking suspected bases of the Kurdish Workers Party in the autonomous Iraqi region of Kurdistan.

"This is a limited operation and not an invasion," an official said. "There will not be a Turkish presence in northern Iraq."

Officials said the operation encompassed about 15,000 Turkish soldiers and reached some five kilometers into Iraq. They said the focus of the operation, which by mid-Thursday was said to have largely ended, was PKK bases in the Kandil mountains.

Ankara has denied any invasion. The United States, which has increased monitoring of the Iraqi-Turkish border, has not confirmed the reports.

"There is no such thing, no entry to another country," Turkish Foreign Minister Abdullah Gul said. "If such a thing happened, then we would announce it."

The military said it has closed the provinces of Hakari, Sirnak and Sirt amid a border security operation. The military statement did not elaborate.

Turkey's Zaman daily, quoting military sources, said a "hot pursuit operation" of PKK operatives was taking place in northern Iraq. The newspaper said the operation consisted of "around 10 Turkish soldiers."

"But reliable military sources stated that Turkish soldiers have on and off entered into a limited area in northern Iraq mainly controlled by the PKK to pursue terrorists escaping from Turkey," Zaman said on Thursday.

Since 2005, officials said, Turkish special forces have been entering Iraq on a regular basis for reconnaissance and other intelligence missions. They said Turkey also maintains a presence of military observers in northern Iraq.

Throughout 2007, the military has been pressing the government of Prime Minister Recep Erdogan to order the elimination of PKK bases in northern Iraq, officials said. Over the last two weeks, Turkey amassed 60,000 troops along the Iraqi border. The troops have been supported by helicopters, unmanned aerial vehicles, main battle tanks and armored personnel carriers.