Controversial referee Tom Henning Ovrebo was understood to have been smuggled out of the country by police after receiving a number of death threats.
Ovrebo has become the target of a hate campaign after failing to award Chelsea a penalty during their Champions League semi-final against Barcelona at Stamford Bridge.
The Norwegian official turned down four penalty appeals - two for clear handball - and Chelsea crashed out of the competition when Andres Iniesta scored a 93rd-minute away goal.
Chelsea had been minutes away from a repeat of last year's final against Manchester United when Iniesta struck. But his strike cancelled out Michael Essien's ninth-minute opener and wrecked Chelsea's dreams of appearing in the final in Rome at the end of May.
After the game, Ovrebo was barracked by the Chelsea players, including Didier Drogba and Michael Ballack and he was escorted to the tunnel by Chelsea stewards.
Police were said to be so concerned about his safety that they changed his hotel before organising his secret exit from Britain.
Police in Ovrebo's home city of Oslo said they were investigating threats made on the internet.
An Oslo police spokesman said: ''We are watching closely what is being posted on the internet. Anything we believe would threaten his personal safety will be taken seriously.''
Former international referee Graham Poll said: ''This morning he's being smuggled out of our country under police escort - this is a referee of a football match. That is a disgrace.
''When he booked in a hotel they had to change the hotel he was staying at because of the fear that maybe fans would find him.''
UEFA have reportedly imposed a gagging order on the official. "Because of the circumstances after the match, Uefa has asked us not to comment to the press," Ovrebo told Aftenposten.
When asked if he knew when he could speak about the match, Ovrebo said: "No, I don't know."
Meanwhile, Chelsea have condemned the actions. "Following media reports claiming threats have been made against the referee of last night's game, Chelsea Football Club would like to make clear that it condemns any form of threat against players, officials or supporters," the club said in a statement.
"If provided with proper evidence Chelsea will take the strongest action against any season ticket holders or members who have participated in this activity.
"Everybody connected with Chelsea is very disappointed with the events of last night. However we would stress that we have received no evidence that Chelsea fans are involved in any of the alleged threats reported."
"As a result of these reports we have also been in contact with the police who likewise had not received any complaints."
The campaign against Ovrebo has echoes of the case of Anders Frisk. He faced a hate campaign after refereeing another game between the two clubs.
Chelsea's coach at the time, Jose Mourinho, accused the official of ''adulterating'' the outcome of a match. Frisk eventually quit the game.
Ovrebo, 42, works as a psychologist outside football. In Euro 2008 the Italian Football Federation demanded an apology from UEFA after he incorrectly ruled out a goal by Luca Toni in Italy's match against Romania Afterwards, Ovrebo admitted he had made a mistake and was not assigned any more tournament matches.
Chelsea full-back Jose Bosingwa says he now regrets calling referee Tom Henning Ovrebo ''a thief'' and has retracted his comments.
In a statement issued on behalf of the player to the Portuguese media, Bosingwa said: ''We were all very disappointed and frustrated after the game, but I regret describing the referee as a thief. Having had some time to reflect I would like to withdraw those comments.''
Bosingwa had labelled Ovrebo a ''thief'' after the Norwegian's decisions in last night's Champions League exit at the hands of Barcelona.
Andres Iniesta's stoppage-time equaliser saw Barca progress to the final of Europe's premier club competition but Chelsea claimed they could have had four penalties.
Bosingwa originally laid the blame for the Blues' failure to reach their second successive final squarely at the official's door.
''I don't know if he's a referee or a thief,'' he told Portuguese television station RTP. ''I don't have any words to describe that man that was on the pitch.
''We have nothing against Barcelona's goal but the penalties that he didn't give us and his way of managing the game weren't right at all.
''This referee should never referee a game again. What happened was a disgrace. It was a well contested game but the referee came to spoil our game.''
Meanwhile Barca coach Pep Guardiola has praised captain John Terry for his behaviour after last night's semi-final defeat.
Despite Terry's disappointment, he visited the Barcelona dressing room and shook hands with each member of their playing and coaching staff. It was an act of sportsmanship for which the Barca team and staff applauded him out of the room.
''I want to thank John Terry for coming into the dressing room and congratulating us,'' said Guardiola. ''He's a true gentleman.''