Nemat Ali Shah was seriously wounded rushed to hospital after being attacked from behind by an unidentified person, rtl website reported.
The incident took place outside his house when he was walking to the mosque.
Hospital sources said Ali Shah is recuperating after a surgery.
A police investigation is going on to find the perpetrator. A police spokesperson said it is too early to talk about the motivation behind the violent assault.
The Pakistani-born Imam had been the target of an attack inside the mosque last year, too.
About two percent of the 5 million residents in Norway are Muslims.