German officials said they were relying largely on American and Pakistani intelligence to identify men who traveled to Waziristan, and while they declined to specify the nature of that intelligence, they said it was strong.

The amount of training under way in the tribal areas of Pakistan is difficult, if not impossible, to estimate, but intelligence officials are concerned about what they see as a trend toward terrorist groups recruiting Westerners.

In a speech in New York on Friday, the C.I.A. director, Gen. Michael V. Hayden, said, “We do see them working to train people whom you and I wouldn’t raise an eyebrow about if they were getting off the plane with us at Kennedy, people whose identity makes it easier — whose persona makes it easier for them to come into America and to blend into American society.”

The Pakistani government has recently acknowledged that Al Qaeda and other militants are operating in the tribal-controlled areas on its border with Afghanistan. Pakistan had struck an agreement with leaders in the South Waziristan tribal area, giving groups there amnesty as long as they refrained from attacking government installations and vehicles. But it broke down last month when the military began a new operation against the militants, which led to the capture of close to 300 Pakistani troops by the militants.

Even as Western governments and Pakistan try to crack down on terrorist training, their efforts are clashing with human rights groups in Pakistan that are pressing for the release of terrorism suspects who have been detained without being charged.

Pakistani courts recently released two Germans, who officials say they believe received explosives training in Waziristan, including a 45-year-old gem dealer who was designated a “potentially dangerous person” by the German police for threatening statements he made three days after the Sept. 11, 2001, attacks. He is back home in Germany, where officials say he has contacts with violent Islamic cells and has made several trips to the border area between Pakistan and Afghanistan.

He was arrested on June 18 by the Pakistani military intelligence agency, Inter-Services Intelligence, or ISI, as he was boarding a plane in Lahore to fly back to Germany, and remained in detention for two months until the Supreme Court ruled there was insufficient evidence to continue holding him.