Osama bin Laden may have lived in Pakistan for over seven years before being shot dead by U.S. forces, senior Pakistani security officials said on Saturday, a disclosure that could further anger key ally Washington over the presence of enemy number one in the country.

One of bin Laden's widows told Pakistani investigators that he stayed in a village for nearly two and a half years before moving to the nearby garrison town of Abbottabad, where he was killed on Monday.

The wife, Amal Ahmed Abdulfattah, told investigators earlier that bin Laden and his family had spent five years in Abbottabad, where one of the most elaborate and expensive manhunts in history ended.

"Amal (bin Laden's wife) told investigators that they lived in a village in Haripur district for nearly two and a half years before moving to Abbottabad at the end of 2005," one of the security officials told Reuters on condition of anonymity.

Abdulfattah, along with two other wives and several children, were among 15-16 people detained by Pakistani authorities at the compound after the raid.

Pakistan, heavily dependent on billions of dollars of U.S. aid, is under heavy pressure to explain how bin Laden could have spent so many years undetected a few hours drive from its intelligence headquarters in the capital.

Suspicions have deepened that Pakistan's pervasive Inter-Services Intelligence (ISI) spy agency, which has a long history of contacts with militant groups, may have had ties with bin Laden -- or that at least some of its agents did. The agency has been described as a state within a state.

Pakistan has dismissed such suggestions and says it has paid the highest price in human life and money supporting the U.S. war on militancy launched after bin Laden's followers staged the September 11, 2001, attacks on America.

Security officials said Pakistan had launched an investigation into bin Laden's presence in the South Asian country seen as critical to stabilizing neighboring Afghanistan.

"It is very serious that bin Laden lived in cities (in Pakistan)... and we couldn't nail it down fully," said one of the officials.

Pakistani leaders were already facing staggering problems before revelations that bin Laden was in their backyard raised new questions about their commitment to fighting militancy.

'WEAKNESS OF OUR RULERS'

Al Qaeda-linked Taliban militants who seem to stage suicide bombings at will remain a major security threat despite several military offensives against their bases in the forbidding mountainous border region between Pakistan and Afghanistan.

The economy is stagnant and the government must impose politically unpopular reforms to keep money from an $11 billion International Monetary Fund loan flowing to Pakistan.

Pakistanis are growing impatient with high food prices and poor services and an education system that is so flawed that many parents are forced to send their children to Islamic seminaries that spread hard-line ideologies that fuel militancy.

Some attention may shift to Chak Shah Mohammad, where bin Laden's wife said he lived before shifting to his last hideout.

The small village of mostly brick clusters of three or four houses also contains cave-like dwellings previously inhabited by the poor that are now being used to keep animals.

People there, like in other areas, expressed disdain for Pakistan's powerful military because bin Laden had spent so much time in Pakistan without being caught or killed.

Such criticism was rare before bin Laden's death put Pakistan under the international spotlight.

"It's a weakness of our rulers, military and intelligence that he (bin Laden) was in Abbottabad and they didn't know that," said Qazi Shaukat Mehmood, who like other residents highly doubts that bin Laden could have lived in Chak Shah Mohammad unnoticed for any length of time.

"I'm here for more than 20 years. I never saw any unusual activity. I don't believe this is true. It must be some kind of joke."

That would please Pakistani officials.

Anger and suspicion between Washington and Islamabad over the raid in Abbottabad, 30 miles from the Pakistani capital, showed no sign of abating.

The New York Times on Saturday quoted Pakistani officials as saying the Obama administration had demanded Pakistan disclose the identities of some of its top intelligence operatives as Washington seeks to find out whether they had contact with bin Laden or his agents before the raid on his compound.

The officials were providing details of what the Times called a tense discussion between Pakistani officials and a U.S. envoy in Pakistan on Monday.

A Pakistani security official denied the report, which he called "malicious."

Many in Washington suspect Pakistani authorities had been either grossly incompetent or playing a double game in the hunt for bin Laden and the two countries' supposed partnership against violent Islamists.

As it engages in damage control over bin Laden's presence, Pakistan must prepare for the possibility that supporters angered by bin Laden's death will hit back.

Since al Qaeda has ties with the Pakistani Taliban, this country could make an easy target.

Al Qaeda has acknowledged that bin Laden is dead, dispelling doubts by some Muslims the militant group's leader had really been killed by U.S. forces, and vowed to mount more attacks on the West.

The announcement on Friday by the Islamist militant organization appeared intended to show its followers around the globe the group had survived as a functioning network.

In a statement online, it said the blood of bin Laden, "is more precious to us and to every Muslim than to be wasted in vain.

"It will remain, with permission from Allah the Almighty, a curse that hunts the Americans and their collaborators and chases them inside and outside their country."

Al Qaeda urged Pakistanis to rise up against their government to "cleanse" the country of what it called the shame brought on it by bin Laden's shooting and of the "filth of the Americans who spread corruption in it."

In Washington, a U.S. official said U.S. intelligence had established on-the-ground surveillance in Abbottabad in advance of the raid. A phone call last year to a man known as the main courier to bin Laden helped lead the CIA to the compound, The Washington Post reported on Saturday.

U.S. officials also said among materials found at bin Laden's hide-out was evidence indicating al Qaeda at one point considered attacking the U.S. rail system on the 10th anniversary of the September 11 attacks.