Martin Hansson, who awarded Liverpool a controversial stoppage-time penalty in the Champions League tie against Atletico Madrid, claimed he has received death threats. The Swedish official was forced to change his phone number but was not specific about the origin of the alleged threats.
He told the Daily Mail: "They threatened me with death, calling me all the time and sending many messages. I am normal but this time it was too much and the tone was bad. I've had enough, it's that simple."
Hansson said he considered quitting refereeing because of the alleged threats but decided to continue.
"It is not worthwhile to be able to influence all this, one does refereeing because of enjoyment.
"I am going to continue believing that football can be good. It would be sad if these dark forces are the ones that win.
"It seems to me that it is very rare that anything positive is said about referees, only when there is some doubt, then everyone says bad things.
"It is normal to emphasise that a large error has been made, but to go on about it for days and weeks is too much."