Iranian authorities on Monday hanged a post-graduate student studying in Tehran who was charged with collaborating with the CIA and Israel's Mossad intelligence service.

The student, Erfan Shakourzadeh, 29, is the fifth person to be executed on espionage charges since Iran's war with the U.S. and Israel began in late February, according to CBS News.

The Norway-based Iran Human Rights Monitor and Hengaw Organization for Human Rights said Shakourzadeh was a student at the prestigious Iran University of Science and Technology in Tehran. He'd been held in solitary confinement, tortured and forced to give false confessions, according to Iran Human Rights, saying the charges were fabricated. 

Hengaw shared a note Shakourzadeh wrote from prison prior to his execution, saying the charges against him were false and that he was tortured into giving his false confession. 

"Do not let another innocent life be taken in silence," Shakourzadeh wrote, according to Hengaw.