A Rangers supporter threatened to bomb Celtic manager Neil Lennon on social networking site Facebook because he "doesn't like him".
Allan McCormack, 25, posted the message "Bomb Neil Lennon, bomb him now" after a Glasgow derby the previous month.
He was caught when police anti-violence teams spotted the message while monitoring the internet.
McCormack, of Colebrook Street, Glasgow, pled guilty to behaving in a threatening or abusive manner by posting the message on April 30, 2011, which was offensive and threatened Mr Lennon with violence.
Glasgow Sheriff Court was told on Thursday that Strathclyde Police's violence reduction co-ordination unit were involved in an inquiry into online hate messages directed at Mr Lennon.
Procurator fiscal depute, Angus Crawford, prosecuting said: "Whilst monitoring social networking sites particularly Facebook, the phrase 'Bomb Neil Lennon, bomb him now' was discovered."
He added they were able to establish McCormack as a suspect and in August last year, telephoned him. McCormack volunteered to go to the police station for an interview where he made admissions about the message posted.
The court was told McCormack claimed to the police he had been drunk and posted the message at 2am on the day after his birthday. It followed a game between Rangers and Celtic in March 2011.
Mr Crawford added: "He further went on to state to police that the posting was in response to a Rangers versus Celtic game at Celtic Park.
"He stated that he didn't like the way Neil Lennon the Celtic manager had conducted himself that day and that he doesn't like Neil Lennon generally."
The court heard McCormack was an "avid Rangers supporter" and often attends games. Sheriff Charles McFarlane QC deferred sentence until next month and continued bail in the meantime.
As conditions of his bail he must sign in at his local police office during the first half of every Rangers game and is not allowed to enter Ibrox Stadium, Celtic Park or Hampden Stadium.
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