U.S. airstrikes early this morning hit the mountain stronghold in northern Iraq of an Islamic extremist group allegedly allied with al Qaeda, according to Kurdish officials, and on Friday targeted the oil centers of Kirkuk and Mosul.

The airstrikes against Ansar al-Islam struck bunkers and checkpoints in a remote corner of the Halabja Valley, about 35 miles southeast of here near the Iranian border. A commander with the Kurdish militia allied with the United States said the U.S. assault began with five detonations from what appeared to be cruise missiles. U.S. Special Forces troops also were known to be in the area, which was closed to reporters in advance of the attack.

Several thousand Kurdish militiamen had massed in the area over recent days in anticipation of the airstrikes, which local commanders said would ease the way for a militia ground offensive against the estimated 900 militant fighters dug into the Shram Range.

Kurdish officials, who have ruled this section of northern Iraq since 1991 under the protection of U.S. and British fighter patrols, called the strike against Ansar just one more component in a U.S.-led war on terrorism.

"Terrorism is an international problem and requires an international response," said Barham Salih, prime minister of the half of Kurdish self-governed territory administered by the Patriotic Union of Kurdistan. "Ansar al-Islam are part of the international terror network."

The Kurdish autonomous zone in northern Iraq area has been a haven for U.S. intelligence teams operating discreetly there for months, preparing two lengthy but spartan airstrips and making other preparations to open a northern front against Saddam Hussein's forces.

Turkey's refusal to accommodate a large U.S. infantry force caused Pentagon planners to reassess their original plans, and the NATO ally's delayed approval of overflight permission has kept even contingency plans off balance.

Reporters sighted a few U.S. Special Operations forces along the line between Bardarasha, east of Mosul, and the town of Kalek to the southwest. The U.S. troops were attached to about a dozen Kurdish units specially trained for infiltration behind Iraqi lines. But the numbers of Americans present, estimated by Kurdish officials to be about 60, is far below the necessary strength to storm the cities of Mosul or Kirkuk. The Pentagon had wanted a force of 62,000 troops in northern Iraq.

Kurds are eager for Kirkuk's liberation from Iraqi forces. Tens of thousands of refugees, driven out of the city by Saddam Hussein's long-standing policy of expelling Kurds and settling Iraqi Arabs, are poised to return.

Kurdish officials reported one setback for their own plans to assist U.S. offensive operations in the north. Iraqi security forces rounded up 61 Kurdish men this week and executed them by firing squad at the Iraqi-held Khalid Camp, said Salih of the Patriotic Union of Kurdistan.

Another Kurdish official said the men were members of a Kurdish underground group making preparations to seize control of Kirkuk from Hussein's government, in a reprise of the 1991 uprising during the closing days of the Persian Gulf War. The plotters were found out when Iraqi security forces discovered two of them with satellite phones the official said were paid for by the United States.

"We still have plenty of people inside Kirkuk," the official said.

U.S. military teams were visible scouting Iraqi front lines Friday at two points on the long front that separates the Kurdish zone from the Baghdad-controlled side. One team trained binoculars on Iraqi bunkers and armor positions on a ridgeline less than a mile above Chamchamal, a Kurdish-held border town about 25 miles east of Kirkuk.

Another team assayed Iraqi positions at Kalar, a crossing point about 50 miles northwest of Al Mansuriyah, where an army headquarters was hit Friday.

The beginning of the war has tantalized Kurds hoping to return to their places of origin. Amin Hussein, an old farmer, stood on a hill less than a mile from the village of Hazer, northwest of Kalek. Hazer is in Iraqi hands, and Hussein claimed that wheat fields belonging to him had been confiscated 28 years ago, during another Kurdish uprising. "We will go right back as soon as the Iraqis leave," he said. Hussein expected Arab settlers in Hazer to flee.

Everyone was on the lookout for American troops. "No soldiers yet," Hussein said. "But we've had plenty of reporters come by."

U.S. airstrikes on Friday also targeted Khalid Camp, a huge military complex southwest of Kirkuk, a city of about 1 million people and the hub of an oil-rich province. The complex lies along the main highway leading south to Tikrit, the home town and tribal base of President Saddam Hussein.

Fatih Kamorosh, a tribal leader in a village northwest of the city, told reporters he was awakened at 5:45 a.m. and counted 30 explosions.

"There seems to have been heavy casualties at the garrison," said a senior official in the autonomous Kurdish zone that begins just 25 miles north and west of Kirkuk. The city was hit three more times after dark, the third strike igniting a fire visible from 20 miles away.

The headquarters of the Iraqi army corps based in Al Mansuriyah, about 50 miles northwest of Baghdad, was hit as well, according to Kurdish commanders.

Detonations were also visible Friday morning and Thursday night in Mosul, the third-largest city in Iraq and the northernmost major population center in the section of Iraq controlled by Hussein's government.

Williams reported from Bardarasha.

The night sky outside of Kirkuk, a city near the Kurdish autonomous zone in northern Iraq, is illuminated by war. Many Kurds hope U.S. air assaults in the area signal they can soon reclaim their land of origin.