Al-Qaeda leader Osama bin Laden, during his years hiding in Pakistan, worried that Iranian officials might implant tracking devices on his sons, according to a document released on January 19.
"If they inject you with a shot, this shot might be loaded with a tiny chip," bin Laden wrote in an undated letter to his sons, Uthman and Mohammed, who were being allowed to leave Iran.
"The syringe size may be normal, but the needle is expected to be larger than normal size. The chip size may be as long as a seed of grain but very thin and smooth," he said.
The letter and other documents were seized when U.S. special forces entered bin Laden's compound in Abbottabad and killed him in 2011.
Documents released last March showed bin Laden expressed the same paranoia in a letter to one of his wives, who also lived in Iran.
"I was told that you went to a dentist in Iran and you were concerned about a filling she put in for you," bin Laden wrote. He said he wanted to be told of any concerns she or any of his followers had about "chips planted in any way."