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A secret U.S. diplomatic memo released Tuesday by WikiLeaks says Afghan President Hamid Karzai freed dangerous detainees and pardoned suspected drug dealers because they had connections to powerful figures.

The memo, which adds to the multiple allegations of corruption within the Karzai government, said that since 2007 the president and his attorney general authorized the release of 150 detainees, including 29 former prisoners held at the U.S. prison in Guantanamo Bay.

"Both authorize the release of detainees pretrial and allow dangerous individuals to go free or re-enter the battlefield without ever facing an Afghan court," said the document, written on Aug. 6, 2009, by Frank Ricciardone, deputy U.S. ambassador to Afghanistan.

"Despite our complaints and expressions of concern to the Afghan government, pre-trial releases continue," it said.

Karzai's spokesman, Waheed Omar, did not immediately respond to a request for comment. He said on Monday that the release of documents would not strain U.S.-Afghan relations.

The memo said that in April 2009 Karzai pardoned five Afghan policemen caught with 273 pounds (124 kilograms) of heroin because they were related to two heroic figures of the Afghan civil war fought in the mid-1990s.

The policemen were tried, convicted and each was sentenced to 16 to 18 years in prison, but Karzai "pardoned all five of them on the grounds that they were distantly related to two individuals who had been martyred during the civil war," the memo said.

According to the document, Karzai also intervened in the narcotics case of Haji Amanullah, the son of a wealthy businessman and one of the president's supporters.

"Without any constitutional authority, Karzai ordered the police to conduct a second investigation which resulted in the conclusion that the defendant had been framed," Ricciardone wrote.

He wrote that intelligence reports indicated Karzai was also planning to release Ismail Safad, a drug trafficker sentenced to 19 years in jail. Safad was a priority target for the U.S. Drug Enforcement Agency who was arrested in 2005 with large quantities of heroin and weapons.

Abdul Makhtar, deputy director of the Afghan prison department, said Safad was still incarcerated at Pul-i Charkhi prison, the main detention facility in Kabul.