Nacional have apologised to Chapecoense after supporters appeared to make mocking gestures during their Copa Libertadores match about the Brazilian club's tragic plane crash.
During their second-stage clash - which Nacional won 1-0 in Chapeco - some visiting supporters were shown taunting their hosts about the accident that killed 19 of Chapecoense's players in 2016.
In a letter to their opponents, Nacional described the behaviour as "sick" and "horrific" and asked for forgiveness from Chapecoense.
"On behalf of Nacional Football Club, we ask the president our deepest sympathy and deep sense of shame. We urge you to accept our deepest apologies to the horrific gesture," a statement read.
"Unfortunately, many sick minds channel their irrationality to sporting scenarios, and all the teams, not just in our continent, are facing this problem, despite the efforts to fight against them.
"It is a big problem, and difficult to control it, and the institutions are worried that they can't control every single act.
"National made great efforts, as in general the clubs of the continent [have done], to avoid such episodes.
"To be true with this, the institution is working with the appropriate investigations and hope that those responsible receive the most severe penalties.
"They will immediately be banned, between many other sanctions. Between them, the Uruguay Football Association, and the security authorities, will prevent them to go to any sport event."