ISLAMABAD, Pakistan - The twin towers in New York were still smoldering in September 2001 when Pakistan spy chief Gen. Mahmood Ahmed went to Afghanistan with the task of urging the Taliban to hand over al-Qaida leader Osama bin Laden.

The message he actually gave Mullah Mohammed Omar was quite different: "Protect Osama. Hide him. We will help you," according to former Taliban deputy interior minister Mullah Mohammed Khaksar. His version has been confirmed by U.S. officials and former Pakistani spies.

A decade later, the U.S. has raised a stinging question: Did Pakistan's premier spy agency, the ISI, know that bin Laden had been living for at least five years near a military garrison in Abbottabad?

The answer is quite likely yes, according to ex-ISI agents, military men and analysts, but the issue is really who knew and how close they might have been to the top.

A week after Navy SEALS killed bin Laden, the U.S. has demanded the names of ISI operatives from Pakistan to investigate what dealings they may have had with al-Qaida. An ISI official, who spoke on condition of anonymity, said no formal inquiry was being held, and that it was "no one's concern" whether Pakistan investigated how bin Laden had lived under the nose of the military without detection.

At the heart of the matter is the long, complicated relationship between the ISI and various militant groups.

The ISI, which is part of Pakistan's military, has a history of spawning and funding jihadi groups to fight India, in particular for the disputed territory of Kashmir. Pakistan's military relies heavily on these groups in the absence of the conventional might to take on India, said defense analyst Ayesha Siddiqua. For example, Pakistan has hosted training camps for militants and has sent them across the border into India, according to U.S. intelligence reports.

"How else do you fight?" Siddiqua asked. "It is the Pakistan version of private security guards."

However, some of these jihadi groups have links to al-Qaida and share with it a militant Islamic philosophy. Harakat-ul-jihad-Islam, the leader of the Illyas Kashmiri group against India, is also believed by Western intelligence to be al-Qaida's operational chief in Pakistan. And Lashkar e-Taiba, which the U.S. calls a terrorist group, is thought to have close funding and operational ties to al-Qaida.

Former President Pervez Musharraf long ago promised to cut off close ties with militants, but there is no evidence that he followed through. Pakistan also claims that it has purged religious extremists from the ISI over the past decade. The ISI did drop Gen. Ahmed soon after the 9/11 attacks, at the insistence of the United States, and Musharraf has handed over senior al-Qaida operatives such as Khalid Sheikh Mohammed, Abu Zubayda and Ramzi Binalshib to the United States.

In a WikiLeaks diplomatic cable dating to May 12, 2008, a U.S. delegation asked Musharraf for his views on reports that the Pakistan army and ISI were complicit in allowing militant activities to continue. Musharraf did not give a direct response, but talked instead about the job of catching militants. "Musharraf said that it wasn't as easy as it appeared," the cable notes. "The mountainous terrain, poor communications, and local supporters impeded efforts to capture and kill these militants."

Despite his protests, experts say, Musharraf grew up under a religious regime and understands the power of religiously motivated uprisings. If anything, the ISI may be as fundamentalist as ever, partly because military personnel from a time when the army was openly involved with militants still work in operations, Siddiqua said.

The ISI also falls under suspicion because bin Laden went undetected despite the many security guards and officers in Abbottabad, a leafy city of 400,000 people close to Islamabad. Al-Qaida has a history in the area: Senior Indonesian al-Qaida operative Umar Patek was arrested there in January, based on information from a captured al-Qaida member, an intelligence official said. And in 2003, raids were conducted in Abbottabad looking for al-Qaida senior lieutenant Abu Laith al-Libi, who was eventually caught not far away in Mardan in 2005.

Retired military officer Lt. Gen. Talat Masood conceded that some people within the establishment were likely suspicious about the occupants of the whitewashed, three-story house in a middle-class area of Abbottabad. However, Masood said, most would not have considered bin Laden their first suspect, and some may have been bribed to keep prying eyes away. Security officers at airports and border crossings in Pakistan are often bribed to ignore suspicious movements.

"The most charitable explanation you can give is that it was at the local level of the police, or some local authority, or someone who carried a lot of weight and influence in the area," Masood said. "He was paid handsomely to ignore who was living there."

The least charitable version, Masood said, is that bin Laden was given safe haven by former military ruler Musharraf, who was waiting until the appropriate moment to announce his capture. Civilian critics in Pakistan accused Musharraf of secretly aiding Taliban militants on both sides of the border, even as militants routinely accused him of siding with the West.

Some analysts and intelligence officials questioned whether top ISI officials would have a good motive to hide bin Laden. It would not in any way help Pakistan, said Brig. Asad Munir, former ISI head for the frontier until 2003.

"You at least have to look at motive...what does bin Laden have to offer?" Munir asked. "It doesn't make sense."

Christine Fair, an academic expert who studies Pakistan and militant groups, agreed that the top leadership of the ISI was likely ignorant rather than complicit in the hiding of bin Laden.

"I really don't believe they knew," said Fair, assistant professor at the Center for Peace and Strategic Studies at Georgetown University in Washington, who has done extensive research in the region.

However, lower-level ISI operatives may well have been aware of bin Laden's presence, Fair said.

She cited the example of the 2008 Mumbai attacks, in which two junior ISI spies were disciplined for knowing about and possibly being involved in the operation. There is no evidence that knowledge of the attacks, which killed 166 people, extended higher up in the ranks.

Mosharraf Zaidi, a private consultant in Pakistan who advises governments on public policy, said essentially the same thing.

"I think there are people who would have known, but did the leadership know? The prime minister, the president, the army chief and intelligence chief?" he asked. "I don't believe so."

If the top officials really did not know, that suggests an incompetence on the part of the ISI shocking to many in Pakistan.

The agency is thought to have about 30,000 people, under six major generals and one lieutenant general. Its financial numbers are secret, but it doesn't have the budget for sophisticated listening devices, for example. In some parts of the country Pakistan doesn't even have the technology to monitor cell phones.

"In general the ISI has an exaggerated profile of its capabilities," wrote Shuja Nawaz, director of the South Asia Center at The Atlantic Council, in an email. "It is best in penetrating India. Worst at handling domestic politics."

The latest episode increases the strain between the ISI and the United States, already at a high because of the case of a U.S. contractor accused of killing Pakistanis. In past meetings, Washington has accused Pakistani leaders of harboring terrorists.

"There was certainly a lot of finger-pointing, a lot of accusing us, both in meetings here and in Washington, of being in bed with the bad guys," retired Gen. Mahmud Durrani, Pakistan's former national security adviser, told the AP. "On one or two occasions they were very, very harsh."

Durrani refused to divulge details, such as whether bin Laden was mentioned, citing national security reasons.

The ISI was born more than 60 years ago, with the job of gleaning information, mostly about India, from the army, air force and navy - thus the name, the InterServices Intelligence, or ISI.

In the early 1970s, then-Prime Minister Zulfikar Ali Bhutto created a political cell within the ISI to keep tabs on his political opponents. Bhutto was overthrown in 1977 and hanged two years later.

Gen. Mohammed Zia-ul Haq came to power and, as an Islamic zealot, created a clerics corps in the army. Officers who had once sipped alcohol at the army messes were competing with each other to be seen by Zia at mosques praying, ex-military officers said.

When the Soviet Union invaded Afghanistan in 1979, the ISI worked with the CIA and Islamic rebels. The same rebels later would become Taliban, or join al-Qaida, or be redeployed by the ISI to India, and today some belong to U.S.-declared terrorist groups like Lashkar-e-Taiba.

The answer about whether the ISI really knew about bin Laden's location may finally come from an unlikely source: Bin Laden himself, or rather, his documents. The U.S. is just starting to process a trove of information taken by commandos from the compound occupied by bin Laden, which may be key to many of the puzzles.