The Afghan Taliban is recruiting and training a growing number of foreign fighters, Al Jazeera has learned.

The move comes as David Cameron, the UK prime minister, said British troops could start withdrawing as early as 2011 due to the progress being made in the fight against the Taliban.

During an unannounced visit to Afghanistan's Helmand province on Tuesday, the prime minister said there were "grounds for cautious optimism" that efforts to restore security and governance were sufficiently on track to begin reducing the force level.

Meanwhile, Al Jazeera has obtained video footage of a Taliban camp in Afghanistan's Kunar province, which appears to show foreign recruits being trained to fight alongside the Taliban.

Al Jazeera has not been able to independently verify the nationality of the men who appear in the video.

Al Jazeera's Sue Turton has this exclusive report from Kabul.