A video showing a teenage girl being flogged by Taliban fighters has emerged from the Swat Valley in Pakistan, offering a shocking glimpse of militant brutality in the once-peaceful district, and a sign of Taliban influence spreading deeper into the country.

The two-minute video, shot using a mobile phone, shows a burka-clad woman face down on the ground. Two men hold her arms and feet while a third, a black-turbaned fighter with a flowing beard, whips her repeatedly.

"Please stop it," she begs, alternately whimpering or screaming in pain with each blow to the backside. "Either kill me or stop it now."

A crowd of men stands by, watching silently. Off camera a voice issues instructions. "Hold her legs tightly," he says as she squirms and yelps.