Kabul, Afghanistan — Osama bin Laden and his deputy Ayman al-Zawahiri are believed to be hiding close to each other in houses in northwest Pakistan, but are not together, a senior NATO official told CNN.

"Nobody in al Qaeda is living in a cave," said the official, who declined to be named because of the sensitivity of the intelligence matters involved.

Rather, al Qaeda's top leadership is believed to be living in relative comfort, protected by locals and some members of the Pakistani intelligence services, the official said.

Pakistan has repeatedly denied protecting members of the al Qaeda leadership.

The official said the general region where bin Laden is likely to have moved around in recent years ranges from the mountainous Chitral area in the far northwest near the Chinese border, to the Kurram Valley which neighbors Afghanistan's Tora Bora, one of the Taliban strongholds during the U.S. invasion in 2001.

The area that the official described covers hundreds of square miles of some of the most rugged terrain in Pakistan inhabited by fiercely independent tribes.

The official also confirmed the U.S. assessment that Mullah Omar, the leader of the Taliban, has moved between the cities of Quetta and Karachi in Pakistan over the last several months.

The official would not discuss how the coalition has come to know any of this information, but he has access to some of the most sensitive information in the NATO alliance.

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