From the U.K. Telegraph:

Border officials have reported that a wide range of material made in Iran – including mortars, plastic explosives, propaganda materials and mobile phones – is ending up in insurgents’ hands.
Rahmutallah Safi, the head of Border Police in Herat, an Afghan city on its western border with Iran, said seized material was marked with Persian writing, Channel 4 News reported last night.
“In this place you can see, we have discovered five mines,” he said. “All the international monitors have seen it. You yourselves can check to see which country has made it. You can see the [Persian] marks on the weapons and the type and show it to the world.”
A Taliban commander admitted that the insurgents had grown more dependent on Iran as Pakistan stepped up operations against the group on its territory.
“Day by day the Iranian border becomes more important for us,” he said. “Especially now in Pakistan there are many problems for the Taliban and many of the Taliban have been imprisoned and also they arrest any Taliban who comes out of the[religious schools].

Not to worry, though. A NATO spokesman says Iran’s support for the Taliban is only “limited.”