WASHINGTON (AFP) – US investigators who screened prisoners considered Pakistani intelligence to be a terrorist group, leaked documents said, laying bare the deep mistrust between the two countries' spies.

A secret 2007 US list of "terrorist and terrorist support entities" listed Pakistan's Inter-Services Intelligence (ISI) alongside some 70 other groups including Iranian intelligence, the Taliban, Hamas and Hezbollah.

The list appeared on a memorandum from the controversial US camp for war prisoners at Guantanamo Bay, Cuba and was obtained and released by the anti-secrecy website WikiLeaks.

The exposure of the private US assessment may cause new strains in the relationship between the United States and ISI, which has longstanding ties to militants but has also worked closely with the CIA.

The WikiLeaks release came just as General David Petraeus, the top US officer in Afghanistan, visited Pakistan and the same day President Barack Obama met top aides for a regular review of strategy toward the two countries.

Top US military officer Admiral Mike Mullen visited Islamabad last week where he was unusually blunt, saying that ISI ties to Afghanistan's Al-Qaeda-allied Haqqani network had caused strains with the United States.

In another part of the leaked document, Guantanamo investigators are told that association with the ISI "in the late 1990s up to 2003" was a sign of Taliban or Al-Qaeda affiliation.

Pakistan helped create the Taliban, who imposed an austere brand of Islam on Afghanistan after taking over in 1996. But Pakistan allied with the United States after the September 11, 2001 attacks planned by Afghan-based Al-Qaeda.

Pakistan, which has received billions of dollars in US aid in the past decade, has bristled at suggestions it is playing a double-game, noting that militants have killed thousands of Pakistanis and even attacked the ISI's headquarters.

The leaked documents showed a complex relationship between the ISI and the United States, which has depended heavily on Pakistani intelligence while at the same time maintaining suspicions.

Khalid Sheikh Mohammed, the self-confessed mastermind of the September 11 atrocity and the most prominent prisoner at Guantanamo Bay, was arrested by the ISI and handed over to the United States.

But documents also pointed to Guantanamo inmate Haji Sahib Rohullah Wakil, alleging that the Afghan helped Al-Qaeda members escape into Pakistan and had been given a permit by a Pakistani official for convoys across the border.

A secret document released by WikiLeaks alleged that Wakil "worked in conjunction" with Pakistani intelligence "to undermine the current Afghan government" led by President Hamid Karzai.

In a separate document obtained by The New York Times, interrogators said that Wakil mentioned that the ISI and a Saudi group deposited money in a bank account he jointly maintained in the Pakistani city of Peshawar.

Al-Qaeda guerrillas who fled US-led military action in Afghanistan have set up a virtual safe haven in Pakistan's north Waziristan, a mountainous region that has never been under full control of the Islamabad government.

The United States has relied on unmanned drones to target accused extremists in North Waziristan, infuriating Pakistani leaders who say the attacks violate sovereignty and kill civilians.

The Pakistani military has used force against homegrown Taliban in other areas including the Swat valley after they approached perilously close to Islamabad.

But US officials often voice concern that Pakistan draws distinctions between Islamist movements, with the ISI seen as maintaining ties to militants who are active in Afghanistan and who target historic rival India.