Arsenal winger Pepe was sent off after VAR officials spotted that he had head-butted Leeds’ Macedonian defender Alioski, with referee Anthony Taylor taking a look at the monitor before brandishing the red card.
British media reported that the two players were subjected to racial abuse from rival supporters after the game.
“We utterly condemn the vile abuse directed at Nicolas Pepe and Ezgjan Alioski on social media following our match against Leeds United,” Arsenal said in a statement.
“This is completely unacceptable and we will be working with the police and authorities to do everything we can to trace and prosecute the culprits.”