ISTANBUL, Turkey - Turkish warplanes bombed Kurdish rebel targets in northern Iraq yesterday in the third confirmed cross-border offensive by Turkish forces in less than a week, the military said.

The U.S. Embassy in Ankara said it had been informed before the assault took place, but it gave no further information. The United States and Iraq have urged Turkey to avoid a major operation in the area, fearing such an operation could destabilize what has been the calmest region in Iraq.

The bombing lasted nearly a half-hour yesterday afternoon and was followed by shelling from inside Turkey, the military said in a statement posted on its Web site. It did not say how deep into Iraqi territory the warplanes penetrated or which areas had been shelled.

Security forces in northern Iraq said the bombs fell about 75 miles northwest of Dahuk. No casualties were reported, said Jabar Yawar, a spokesman for Kurdistan's Peshmerga security forces in northern Iraq.

The forces vowed to continue military operations on both sides of the Turkish-Iraqi border "no matter how the conditions are."

On Dec. 16, Turkish jet fighters launched the first confirmed air assault on Iraqi soil since the U.S.-led invasion, bombing bases in northern Iraq held by the separatist Kurdistan Workers' Party, or PKK.

Two days after that assault, Turkey sent hundreds of troops into northern Iraq, but it withdrew them later in the day. The military said the two operations dealt a major blow to the rebels.

In yesterday's statement, it said hundreds had been killed in the operations, citing "intelligence gathered from various sources." It said footage showing the results of the operations would be released in coming days.

Turkish forces periodically have shelled across the border and sometimes have carried out "hot pursuits" - limited raids on the Iraqi side that sometimes last only a few hours.

The rebels have battled for autonomy in southeastern Turkey for more than two decades and use strongholds in northern Iraq for cross-border strikes.

After a surge in rebel attacks in the past months, Turkey has said it can no longer tolerate the attacks on its troops. In October Turkey's parliament authorized the military to strike back at the rebels inside Iraq.