The Islamic State is reportedly planning to build a "joint army" of terrorists in Afghanistan and Pakistan to attack India that will trigger an Armageddon-like 'end of the world', according to a document of the terror group found in Pakistan's tribal areas.

The 32-page document in Urdu, believed to be a "recruitment record", was accessed by the American Media Institute (AMI) from a Pakistani citizen who reportedly has links with the Pakistani Taliban.

The translated version of the document titled "A Brief History of the Islamic State Caliphate (ISC), The Caliphate According to the Prophet" was reviewed by three US intelligence officials who believed the document to be "authentic", says a 28 July news report published in USA Today. 

The unique markings on the document, the writing style and the language used to describe leaders lends credibility to it, according to the officials.

The Isis is planning to "unite dozens of factions of the Pakistani and Afghan Taliban into a single army of terror", which will launch a terror attack on India and "preparations" for it are underway, says the document.

By attacking India, the Isis aims to "provoke an apocalyptic confrontation with America", says the USA Today report, referring to the document. 

"Even if the US tries to attack with all its allies, which undoubtedly it will, the ummah will be united, resulting in the final battle," according to the document. 

Bruce Riedel, a senior fellow with the Brookings Institution, who was with the CIA for more than 30 years, said that an Isis attack on India will "threaten the stability of the region" and "magnify the Islamic State's stature". 

"Attacking in India is the Holy Grail of South Asian jihadists," USA Today quoted Riedel as saying.

The document has been described as a manuscript of "chilling" details where the Isis is urging al-Qaeda to join the terror group, which plans to rule the entire world one day.

"It includes a never-before-seen history of the Islamic State, details chilling future battle plans, urges al-Qaeda to join the group and says the Islamic State's leader should be recognized as the sole ruler of the world's 1 billion Muslims under a religious empire called a 'caliphate'," the USA Today report quotes from the undated document.

Exhorting al-Qaeda for merger, the Isis document says, "Instead of wasting energy in a direct confrontation with the U.S., we should focus on an armed uprising in the Arab world for the establishment of the caliphate." 

In the document, the Isis threatens to "behead" anyone who rebels against Allah.

"Accept the fact that this caliphate will survive and prosper until it takes over the entire world and beheads every last person that rebels against Allah... This is the bitter truth, swallow it," says the document. 

'The document needs to be taken seriously'

Retired Defence Intelligence Agency Director Lt General Michael Flynn has said the document 'needs to be taken seriously' as it contains their intentions.

"The document "represents the Islamic State's campaign plan and is something, as an intelligence officer, I would not only want to capture, but fully exploit. It lays out their intent, their goals and objectives, a red flag to which we must pay attention," said Flynn. 

"They have demonstrated an incredible level of resiliency and they will not be defeated by military means alone," he added.