The Taliban's strength in Afghanistan has increased by up to 20-30 percent over the past year, according to Major General Jeffrey Schlosser, a top general in-charge of US ground troops in Afghanistan.

In a CBS TV interview to be telecast this Sunday, he said evidence of the increase in numbers was apparent on a base in eastern Afghanistan, near the Pakistan border, which has been hit with rockets and mortars at least 30 times since March, when a major battle took place.

He said the enemy had come much closer to his men in the battle, engaging troops in a firefight near their base.

General Schlosser said his soldiers had never been this close to their enemy in Afghanistan before.

After at least 12 enemy fighters were killed in the skirmish, soldiers found a camera left behind by the enemy that contained images of at least 50 heavily armed enemy fighters, showing details of their training and actual attacks.

It also showed enemy surveillance of US soldiers on patrol.