Helicopters ferried troops from the Army's 82nd Airborne Division to the remote, mountainous area as the hunt for Osama bin Laden and his terror network intensified, according to U.S. military officials in Washington.

Military officials in Afghanistan confirmed the operation was underway, but would provide no details.

"I do not have anything to say about the Kandahar operation at this time," said Col. Roger King, U.S. army spokesman at the U.S. headquarters at Bagram.

The troops left from their base in Kandahar, the former Taliban stronghold in southern Afghanistan.

Radio transmissions had been detected coming from caves above the villages, said military officials in Washington .

It was the largest U.S. military operation in Afghanistan since Operation Anaconda just over a year ago. That eight-day battle involved hundreds of Taliban and al-Qaida fighters against thousands of American and allied Afghan troops.

There have been a series of raids on both sides of the Afghanistan-Pakistan border in the weeks since authorities captured al-Qaida's No. 3 figure, Khalid Sheikh Mohammed, in Pakistan on March 1. Authorities have said Mohammed is giving information to U.S. interrogators and have said some of the subsequent arrests came as a result of Mohammed's capture.

Mohammed, an alleged mastermind of the Sept. 11 terrorist attacks in the United States, is being interrogated by American officials at an undisclosed location.

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.