Two Taliban spokesmen said their mobile phones, emails and a website had been hacked and messages issued on Wednesday falsely reporting the death of the movement's supreme leader Mullah Mohammad Omar.
The one-eyed, reclusive leader is one of the most wanted men in the world, and is believed to be living in Pakistan, probably in the city of Quetta. Pakistan and the Taliban movement both deny this and say he is in Afghanistan.
"This is the work of American intelligence, and we will take revenge on the telephone network providers," said spokesman Zabihullah Mujahid, when contacted by Reuters to confirm the veracity of one text message.
The messages came from phone numbers used in the past by both Mujahid and a second spokesman Mohammad Qari Yousuf and said "spiritual Leader Mullah Mohammad Omar Mujahid has died" and "May Allah bless his soul".
Yousuf said the hacking was an attempt at psychological warfare by NATO-led forces.
"The enemies have sophisticated technology so they can easily manipulate our website and our phone numbers. The enemies are spreading rumours because they are facing a decisive defeat and their morale is weakened," he told Reuters.
The death of Mullah Omar was reported in May, by media including Afghanistan's private TV station TOLO. That report was dismissed by security officials in Pakistan and diplomats, US military commanders and government officials in Afghanistan.
With a $10 million US bounty on his head, he fled with the rest of the Afghan Taliban leadership to Quetta after their government was toppled by US-backed Afghan forces in late 2001. They formed the "Quetta shura", or leadership council.
The Taliban were overthrown for refusing to hand over al Qaeda leader Osama bin Laden after the Sept. 11, 2001, attacks on the United States.