“To be clear, the image used perpetuated a racist stereotype,” said Liverpool in a statement sent to CNN. “This is completely unacceptable.”
Hung in the away end of the Luminus Arena in Genk, the banner featured a picture of Origi’s head on a naked body standing next to the Champions League trophy.
It was taken down before the game had kicked off after the club was made aware of its presence.
Liverpool insists it will take action against those responsible for the banner.
“We acted swiftly to have the banner removed and we are now working with the local authorities and stadium team in Genk to identify those responsible,” added the Liverpool statement.
“Any subsequent action will be taken in keeping with our sanctions process.”
Origi, who spent his developing years in the youth set-up at Genk, was named as a substitute for the game in Belgium. He came on in the 80th minute.
Liverpool won the game 4-1 with Alex Oxlade-Chamberlain scoring twice before Sadio Mane and Mohamed Salah got in on the act.
The incident comes at a time where a number of high-profile racist incidents have taken place within the world of football.
Liverpool must now wait to find out if it will be punished by UEFA, the game’s European governing body, for the banner.
The incident soured Liverpool’s victory secured by two goals from Oxlade-Chamberlain, the second of which was a wonderfully executed finish with the outside of his right foot.
Further goals by Mane and Salah completed the win, though Stephen Odey did net a late consolation for the home side.
“All four goals were brilliant and could have scored more,” Liverpool manager Jurgen Klopp told BT Sport. “Job done, perhaps in years before we would have drawn the game or lost. It was intense but (we want) more concentration wise.”
It means Liverpool now has six points from its three group games in Group E, one adrift of leader Napoli which overcame Red Bull Salzburg 3-2 in Austria.