BAGRAM, Afghanistan -- As the war began in Iraq, U.S. soldiers mounted one of the biggest searches in a year for Taliban and al-Qaida fugitives in Afghanistan.

The military said the timing was coincidental, adding that it was acting on new intelligence from radio intercepts. Anti-U.S. groups had threatened to intensify attacks on the multinational coalition in Afghanistan if war broke out in Iraq.

Operation "Valiant Strike" began at 6 a.m. Thursday local time (7:30 p.m. CST Wednesday) and involved nearly 1,000 U.S. troops and their Afghan allies. Backed by attack helicopters, they swept into southern Afghanistan, combing mountain terrain and valley villages.

Military spokesman Col. Roger King said the raids focused on areas east of Kandahar, the former spiritual headquarters of the Taliban, which is allied with al-Qaida, Osama bin Laden's terrorist network.

Khalid Pashtun, a spokesman for the Kandahar provincial government, said the Taliban's supreme leader Mullah Mohammed Omar has tribal links in the area.

"Operations in Afghanistan are conducted completely independent of any operations in other sectors," King told reporters at Bagram Air Base. "We have done a series of major operations; this is one more in a continuing series."

In Washington, officials dismissed suggestions the offensive was intended to show the war against Saddam Hussein was not taking away attention from the war on terror.

"It is not connected and would have been coincidence," Joint Chiefs of Staff Chairman Gen. Richard Myers said.

The military launched the operation after receiving "a mosaic of different intelligence inputs" of activity in the area, King said. Radio signals had been detected coming from areas above the villages, according to military officials in Washington.

Civil affairs specialists, who get to know and befriend local residents, also contributed information leading to the assault.

The operation was led by an 800-soldier battalion known as the "White Devils," part of the 82nd Airborne division, though additional ground support teams and special forces soldiers also were taking part, Army officials said.

Master Sgt. Richard Breach said he had no details on whether the troops, including Special Forces and civil affairs teams, had come across any enemy fighters or made any arrests. There was also no word on casualties.

But Gul Mohammed, head of the district administration who accompanied some of the U.S. forces, told The Associated Press that the group he was with made no arrests after searching hundreds of homes.

The operation was likely to continue for two or three days, said Lt. Coryll Angel, a U.S. military spokesman in Kandahar.

The assault was one of the biggest in Afghanistan since Operation Anaconda just over a year ago, King said. That eight-day battle pitted hundreds of Taliban and al-Qaida fighters against thousands of American and allied Afghan troops.

Since then, the multinational, U.S.-led coalition has carried out at least a dozen major offensives. An operation of similar size took place in neighboring Helmand province about a month ago. Several suspected militants were killed and about 30 were captured.

The latest assault involved Blackhawk, Apache and Chinook helicopters along with armored Humvee vehicles.

A series of raids have been staged on both sides of the Afghanistan-Pakistan border since authorities captured al-Qaida's No. 3 figure, Khalid Sheikh Mohammed, in Pakistan on March 1.

Authorities have said that Mohammed, an alleged mastermind of the Sept. 11 terror attacks, is giving information to U.S. interrogators at an undisclosed location and that some of the subsequent arrests were a result of his capture.

The agents who captured him in a suburb of Islamabad found computers, mobile telephones, documents and other evidence that could help lead to other al-Qaida members.

There have been increased attacks on Afghan government posts in southern Afghanistan in recent weeks. The authorities have blamed remnants of Taliban, al-Qaida and loyalists of Gulbuddin Hekmatyar, a renegade rebel commander labeled a terrorist by the United States.

"There is a heightened awareness on the part of all the soldiers of potential for enemy activities based upon the initiation of hostilities in the Iraq theater," King said.