The incident occurred in the final minute of the match on Aug. 15. With the scores level at 1-1, a 17-year-old youth ran on to the field and chased Keita before knocking him to the ground, causing the game to be abandoned.
"The disciplinary committee's majority believes that the supporter who attacked the Ostersund goalkeeper should be considered a Jonkoping supporter, and for that reason Jonkoping are responsible for what happened and lose the match," the FA said.
Jonkoping director Kjell Lundgren said the club would probably appeal against the decision.
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(Reporting by Philip O'Connor, editing by Ed Osmond)
