The Taliban in Afghanistan have published what they claim is a top-secret government security plan for a major meeting of elders this week, but officials deny the document is genuine.

The "loya jirga" or traditional meeting is due to start in Kabul on Wednesday and will feature about 2,000 elders discussing Afghanistan's long-term relationship with the US plus efforts to make peace in the country.

The alleged plan, published on the Taliban's website late Sunday, features a satellite map of the venue where the event will take place, mobile phone numbers of top security officials and details of security force deployments.

"The vigilant mujahideen of the Islamic emirate (the Taliban) have acquired the security plans, maps and other documents related to the upcoming supposed loya jirga," the militant group said in a statement sent to media.

The Taliban said the documents were seized "by means of its personnel embedded inside the enemy ranks".

The militant Islamists, leaders of a 10-year insurgency in Afghanistan, have already threatened to target the meeting, and struck at Afghanistan's last loya jirga in 2010.

But Afghan government officials and the international military say it is a fake.

"We strongly dismiss this and there is no truth in it," Abdul Rahman Rahman, the deputy interior minister responsible for security and police matters, told a press conference in Kabul.

"If this document were real, they would have used it to attack the loya jirga and later leak it out. If it's real why would you publish it?"

A spokesman for the NATO-led International Security Assistance Force (ISAF), William Truelove, called the document a "fabricated piece of propaganda" and said it was "an attempt to disrupt this peaceful jirga".

Separately, interior ministry spokesman Sediq Sediqqi told journalists that a man believed to be one of the Taliban's main media spokesmen, Zabiullah Mujahid, had been captured in southeast Afghanistan Monday.

However, ISAF spokesman Sergeant Christopher DeWitt cited the deputy governor of Paktika province as saying that while the individual captured had the same surname as the spokesman, it was not the same person.