The discovery indicates that bin Laden used the Pakistan-based terror group HUM as part of his support network inside the country, The New York Times reported quoting US officials.
"It also raised tantalising questions about whether the group and others like it helped shelter and support bin Laden on behalf of Pakistan's spy agency, given that it had mentored Harakat and allowed it to operate in Pakistan for at least 20 years," the daily reported quoting officials and analysts.
"It's a serious lead," said one American official, who has been briefed in broad terms on the cellphone analysis. "It's an avenue we're investigating."
The daily said the revelation also provides a potentially critical piece of the puzzle about bin Laden's secret odyssey after he slipped away from American forces in the Tora Bora region of Afghanistan nearly 10 years ago.
Harakat "is one of the oldest and closest allies of al-Qaeda, and they are very, very close to the ISI," said Bruce O Riedel, a former CIA officer.
The records reportedly show the Harakat had called intelligence officials but it cannot be determined whether these calls were in connection with Bin Laden.
Harakat leaders have strong ties with both al-Qaeda and Pakistani intelligence, and they can roam widely because they are Pakistanis, something the foreigners who make up al-Qaeda's ranks cannot do.
