What is tragedy chanting? Jurgen Klopp's appeal to Liverpool and Manchester United football fans explained

Liverpool manager Jurgen Klopp urged fans of his own club and Manchester United to "show a bit of class" ahead of Sunday's Premier League meeting at Old Trafford as tragedy chanting threatens to once again sour one of English football's great occasions.

Amid United's dramatic and raucous 4-3 FA Cup win over their old rivals last month, two home supporters were arrested in relation to chants referencing the 1989 Hillsborough disaster, where 97 Liverpool fans were killed. One was charged and the other was bailed.

As with many aspects of football fandom, there is a tit-for-tat element to all of this. United have frequently been targeted by terrace chants referencing the 1958 Munich air disaster.

"I think it is super important," Klopp said when asked about the issue at his pre-match news conference. "One aspect is that I don’t hear it, honestly, when I am on the sideline but I get told it happens and that is obviously not great. But in general it is just helpful that we educate our kids in specific things: respect, understanding, all these kinds of things.

"I just see it that way that two of the biggest clubs in the world, let’s just show a bit of class in these moments, so don’t sing this or that. Just show class, have a fight on the pitch, let's just play football. If you want be happy, if you lose, whatever but besides all of that just show a bit of class, that would be my wish really for all of us.”

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In the immediate aftermath of Chelsea's 0-0 draw with Liverpool at Stamford Bridge last season, the London club issued a statement.

"Chelsea FC condemns the inappropriate chants heard from some home fans during this evening's game," it read. "Hateful chanting has no place in