An intense Pakistani military operation directed at suspected al Qaeda hideouts along the Afghan-Pakistan border has led to the seizure of a number of al Qaeda suspects and the discovery of a cache of computer information that contributed to last weekend's decision to increase the terror alert in several U.S. cities, Pakistani officials said Thursday.

The Pakistani operation has employed sophisticated American eavesdropping technology and computerized identification systems, they said. Three wanted al Qaeda operatives have been arrested, and computer files were found with detailed surveillance reports on terrorist targets and information about the whereabouts of other al Qaeda members, according to the officials.

The military effort has forced the fighters out of the rugged remote tribal areas, just inside Pakistan, and into more urban areas, where they are more visible and vulnerable to capture, they said.

The operation is being paid for with millions of dollars from the CIA, supported with equipment from the National Security Agency and carried out by Pakistani soldiers and intelligence units. It has netted more than 100 suspects in recent days, the officials said. Eighteen detainees have been identified by the officials as al Qaeda members, according to Faisal Saleh Hayat, Pakistan's interior minister.

"We have a bead on some people," a U.S. military officer said in a comment echoed throughout the U.S. government on Thursday.

The heightened security alerts in the United States came after data seized in Pakistan suggested that the group was targeting five financial buildings in New York, Washington and Newark.

One Pakistan intelligence official said: "U.S. assistance comes in the shape of incredible data and analysis based on electronic and signal intercepts of al Qaeda suspects all over the world. Their information is also based upon the detailed debriefing of the arrested suspects and a scientific follow-up of these debriefings held at unidentified locations."

In London, Scotland Yard announced the arrest of Babar Ahmad, a British subject of Pakistani descent, on a U.S. extradition request from the U.S. District Court in Connecticut. Ahmad, 30, is accused of soliciting funds and property through the Internet for "acts of terrorism in Chechnya and Afghanistan," including political murder between 1998 and the end of 2003, U.S. officials said. They said that Ahmad had been under surveillance for several years but that information obtained in other counterterrorism operations in the past week allowed them to make the arrest.

Late Tuesday, British authorities arrested 12 people, including a key al Qaeda figure, Eisa Hindi, and several others who have since been identified as members of the organization. According to U.S. officials, Hindi is suspected of helping to produce, before the Sept. 11, 2001, attacks on the United States, the surveillance of the five buildings that led officials on Sunday to raise the terror alert level.

Also on Thursday, Saudi Arabia's security forces arrested a leading militant, Faris Zahrani, Saudi-owned al-Arabiya television reported. The report said Zahrani did not resist when he was arrested in southern Saudi Arabia. Zahrani was on a list of that country's 26 top wanted militants with suspected links to al Qaeda.

Meanwhile, a Pakistani intelligence officer said that "there was a definite link" between a June 10 attack on a Pakistani corps commander, in which 11 troops were killed, and the arrest two days later of Mussad Aruchi, a suspected al Qaeda operative. The commander, Lt. Gen. Ahsan Saleem Hayat, was not hurt.

Aruchi is reportedly a nephew of Khalid Sheik Mohammed, one of the planners of the Sept. 11 attacks. Aruchi was arrested in Karachi on June 12. The operation was supervised by the CIA, and the agency provided crucial information indicating his location, Pakistani intelligence sources said.

Aruchi possessed information about U.S. financial targets as well as the names of his associates. He had old street maps of New York City and addresses of other significant buildings, along with a number of compact disks containing information useful to investigators.

Aruchi's arrest, according to Pakistani officials, led authorities to Muhammad Naeem Noor Khan in the city of Lahore on July 13. Khan's e-mail traffic has helped lead authorities to other al Qaeda suspects.

The interrogations of Khan and Aruchi then led officials to Ahmed Khalfan Ghailani, who was captured on July 25. Ghailani is a Tanzanian wanted by the United States in connection with the 1998 bombings of the U.S. embassies in Kenya and Tanzania. A laptop computer seized with him contained maps and messages, apparently from scouts who had entered some of the targeted locations in the United States.

These documents were produced before the Sept. 11 attacks. U.S. officials have said they included updated information on one building as late as January 2004, but the officials were not certain whether it amounted to new surveillance or whether it was information publicly available.

In most cases, Pakistani officials said, once suspects have been captured, the CIA has taken control of the interrogations and custody of the computer files and other documents.

The intensity of the recent fighting in Waziristan, a northwestern tribal region bordering Afghanistan, has surprised Pakistani officials. Thousands of troops have been fighting in Waziristan for two months, when the military launched an offensive against the suspected hideout of Osama bin Laden's deputy, Ayman Zawahiri. Although Zawahiri has not been located, the fierceness of the resistance indicated to Pakistan troops that they were likely attacking an area populated by major al Qaeda suspects.

"We had fairly solid intelligence that at least Ayman al Zawahiri was roaming in this region," said a senior Pakistani intelligence official. "Once we penetrated the area, we didn't find Zawahiri, but we definitely confronted and killed many future Zawahiris in this area."

"The Pakistanis are pounding away at Waziristan," one senior U.S. national security official said.

Thirteen Pakistani troops, including three officers, were killed Thursday when a military helicopter crashed in Waziristan, near the garrison town of Kohat. A suicide bomber attacked the house of a senior military commander in the town last month, killing two senior intelligence officials. At least 100 Pakistani troops and 200 people, including local tribesmen, non-Pakistani Arabs and other foreigners, have been killed in the region. Authorities said hundreds of people have fled their homes.

After a fierce rocket attack Wednesday night on military checkpoints in the tribal town of Shikai, authorities imposed economic punishment on the community, restricting the flow of local produce -- apricots, plums and dry fruit -- into local markets.

"The situation is still explosive because al Qaeda elements and their local supporters are running hit-and-run operations in a different terrain," said a Pakistani intelligence officer based in Peshawar.

Priest reported from Washington. Correspondent Glenn Frankel in London contributed to this report.

A Pakistani paramilitary soldier takes position in a bunker in the volatile Waziristan tribal region, near the Afghan border.