Amin al-Haq was detained in Lahore three years ago by the Inter-Services Intelligence (ISI) agency. He had escaped from Afghanistan with the Al Qaeda leader in 2001 and went on to become a key financial aide.
The ISI had passed al-Haq on to the police before he was released earlier this month, The Telegraph newspaper reported Thursday quoting a security source in Peshawar, where he had been held.
"Amin al-Haq had been arrested mistakenly, therefore, the police failed to prove any charge of his association with Osama bin Laden and the court set him free," he told the Telegraph.
Al-Haq, who is thought to be 51, has a long history with armed groups. He fought Soviet forces during the 1980s and was part of the Afghan delegation, which travelled to Sudan in the 1996 to bring Osama to Afghanistan.
The US froze al-Haq's assets after the 9-11 attacks on the World Trade Centre, according to the newspaper.
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