Afganistan - Taliban leader Mullah Omar says his fighters are winning the war in Afghanistan and that the Nato-led campaign has been "a complete failure".

In a rare statement, the elusive leader called on US President Barack Obama to withdraw his troops "unconditionally and as soon as possible".

Nato has boosted its presence in Afghanistan to 150,000 soldiers in a bid to finally defeat militants.

However, the US has set July 2011 to begin withdrawal, if conditions allow.

Critics of the move say it has emboldened the Taliban.

Mullah Omar's statement, which marked the end of the Muslim festival of Ramadan, was posted on jihadist websites and relayed by the Site Intelligence Group.

"The victory of our Islamic nation over the invading infidels is now imminent and the driving force behind this is the belief in the help of Allah and unity among ourselves," he said.

"In the time to come, we will try to establish an Islamic, independent, perfect and strong system."

He claimed that those behind the 2001 invasion of Afghanistan which overthrew the Taliban "admit themselves that all their strategies are nothing but a complete failure".

He also commanded his fighters to observe the Taliban's code of conduct and avoid harming civilians.