Afghan and Western officials have accused Iran of delivering tonnes of weaponry to the Taleban, including plastic explosives, mortars, grenades and technical manuals.

According to The Times, weapons and documents shown to Channel 4 News indicate that more than ten tonnes of weapons have been intercepted at Iran's desert border with Afghanistan in the past year, with a tonne and a half recovered in the past week.

The reports come as General David Petraeus, the head of US Central Command, warned the Senate Foreign Relations Committee that Iran also provided a base for al-Qaeda operatives.

Afghanistan's intelligence agency estimates that 60 per cent of the weaponry it has intercepted from Iran has been supplied by the Iranian Government rather than black market dealers.

Allegations of Iranian support for the Taleban, using secretive units of the Quds (Revolutionary Guard) have been made in the past.

In 2007 General Dan McNeill, then the commander of NATO forces in Afghanistan, claimed that a consignment of roadside bombs was intercepted by British special forces crossing into Farah province from Iran.

The Taleban and its al-Qaeda allies have been on the back foot in recent months, as the US military surge and increasingly successful attacks from unmanned drones decimated their leadership. (ANI)