"Salem was attacked by Mustafa Dossa with sharp object. He was injured and doctors are treating him inside the jail. A police team is at the spot," Vasant Tajane, Senior Inspector at N M Joshi Marg police station, said.
42-year-old Salem, a key accused in the 1993 serial bomb blasts, has been lodged in the South Mumbai jail since his extradition from Portugal in 2005.
He is currently housed in barrack number 10 of the jail along with scores of other prisoners.
Salem is facing trial in nine cases, including two murders.