According to the BBC, officials in Afghanistan are concerned that the Taliban are now fighting with weapons obtained from China, and that Iran may be playing the intermediary:
The BBC has been told that on several occasions Chinese arms have been recovered after attacks on British and American troops by Afghan insurgents.
The authorities in Beijing have promised to carry out an investigation.
…Unnamed US officials have recently been quoted as saying that China has been selling arms to Iran which Iran is then passing on to insurgent groups in Afghanistan and Iraq. [Full text]
See also “The Arsenal Of The Iraq Insurgency: It’s Made In China“.