Breaking its official silence on the recent arrest of top al Qaeda lieutenant Khalid Sheik Mohammed, Pakistan's secretive Inter-Services Intelligence agency said today that Mohammed told interrogators he met with Osama bin Laden in December but wouldn't tell them where.

In a highly unusual background briefing for foreign journalists here, senior officials from the agency said Mohammed, who was suffering from a high fever, was interrogated for three days by a joint U.S.-Pakistani team before being turned over to U.S. custody.

During the first two days, they said, Mohammed was uncooperative and divulged only his name. On the third day, however, Mohammed "started divulging information on his contacts inside and outside Pakistan," including a meeting with bin Laden in December, one of the officials said.

"He could resist only for two days," the official added.

The official said that based on Mohammed's interrogation and other evidence, investigators believe bin Laden is alive, though probably not in Pakistan. He also questioned the credibility of Mohammed's assertion that he had met bin Laden in December, saying, "I don't believe him unless he tells us the location."

Officials from the intelligence agency, known as ISI, rarely make themselves available to the foreign press. In keeping with their reputation for secrecy, the ISI officials who conducted the briefing declined to give their names. The marble-floored hall outside the briefing room was decorated with photographs of generals and a saying attributed to Gen. George S. Patton: "By way of deception, thou shall do war."

The most powerful of Pakistan's multiple security services, the organization worked closely with Afghanistan's Taliban movement and has provided training and logistical support to Islamic groups fighting Indian forces in Kashmir. But ISI officials said they wanted to counter the impression that the agency was not serious about fighting terrorism or was doing so only because the United States gave it no choice.

"We thought [the briefing] was necessary because this organization is making tremendous efforts to combat terrorism," one of the officials said. "We are not getting our due."

Over tea and sandwiches at their modern headquarters here, ISI officials gave a slide presentation summarizing Pakistan's anti-terror efforts and then played a videotape that they said showed the pre-dawn raid that netted Mohammed and another senior al Qaeda figure, Mustafa Ahmed Hawsawi, in the Islamabad suburb of Rawalpindi this month.

The videotape showed men identified as ISI agents checking their armored vests, boosting one another over a high wall and using bolt-cutters to open a steel gate. That was followed by footage of agents moving into a house with guns drawn, then pressing a man identified as Mohammed against a wall. The man's back was to the camera and a hood was quickly dropped over his head. The tape never showed the man's face.

Other scenes showed armed agents moving from room to room collecting evidence, including a computer, and depositing it into plastic bags.

"We almost recovered a full vehicle load of evidence from the house, which we are in the process of exploiting," said one of the officials, although he said that much of the evidence -- including the computer -- had been shipped to the United States.

One agent was shot in the foot during a struggle with Mohammed, the officials said, but otherwise the raid went without a hitch. The officials said Mohammed looked very different than the bearded man in their photographs and they weren't sure at first whether they had captured him. The officials declined to describe the leads that led them to the house in Rawalpindi.

In showing the tape, the ISI officials appeared eager to demonstrate that their agents conducted the raid without help from FBI agents, who have been present for other al Qaeda arrests in Pakistan. They displayed a photograph that appeared to show Mohammed sitting in an interrogation room with a blanket wrapped around his shoulders; officials said the blanket was to ward off chills from a high fever.

The Washington Post and other news organizations, citing unnamed Pakistani and U.S. officials, have reported that Mohammed was spirited out of the country within hours of his arrest. On the basis of accounts provided by other Pakistani security officials, one of whom was present for Mohammed's interrogation, the Post also has reported that Mohammed told investigators he had not seen bin Laden since before the Sept. 11, 2001, terrorist attacks. The conflicting accounts could not be reconciled.

Besides trumpeting the agency's role in Mohammed's arrest, the officials also used slides to highlight Pakistan's counterterror efforts. They noted, for example, that 442 suspected foreign terrorists had been arrested in the country since the 2001 attacks on the United States. Of those, 346 have been handed over to the United States, 36 to other countries and 55 released; five are still being interrogated, according to the presentation.

Khalid Sheik Mohammed, the alleged mastermind of the Sept. 11 attacks, was interrogated for three days before being turned over to U.S. custody, Pakistani officials say.