Osama bin Laden was said to be staging a defiant stand in the Afghan mountains as Taliban rule finally came to an ignominious end with the surrender of the last province under their control.
A spokesman for the Northern Alliance claimed bin Laden was now leading the defence of his mountain hideouts in person, with about 1,000 fighters from his al Qaeda organisation.
The spokesman, said they had dug themselves into the forests of Spin Ghar after Northern Alliance forces overran all the al Qaeda bases in Tora Bora.
The chairman of the U.S. Joint Chiefs of Staff, General Richard Myers, said the United States knew in general where bin Laden was hiding.
Vice President Dick Cheney said the US wanted to get their hands on both bin Laden and Taliban supreme leader Mullah Mohammad Omar and take them into US custody.
CNN reported al Qaeda fighters had kept up a barrage of mortar fire for several hours on Saturday, cutting a road into Tora Bora and forcing their Afghan opponents' tanks to pull back.
The US launched strikes on Afghanistan in October to try to catch bin Laden and destroy his al Qaeda network, which it claims carried out the September 11 attacks on New York and Washington.