Liverpool have warned any supporters found selling Champions League final tickets through secondary ticketing sites face being banned from attending matches at Anfield.
Demand for tickets for the showpiece occasion against Tottenham Hotspur in Madrid on June 1 has far outstripped the allocation handed to the Reds by UEFA.
Thousands of supporters who has applied for a seat were left disappointed on Thursday when the results of the ballot to determine who has been successful in having access to a ticket were revealed by the club.
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However, within hours hundreds of the limited tickets allocated to fans began appearing on resale sites for eye-watering prices that range from €3,000 (£2,619) to €40,000 (£35,000).
And Liverpool are determined to stop fans from paying over the odds for the game at the Estadio Metropolitano.
A club statement said: "Liverpool FC has issued advice to supporters on the sale and purchase of Champions League final tickets via secondary and unofficial ticketing sites.
"Fans are warned that buying tickets via unofficial online sources does not guarantee tickets are genuine or that they will actually receive them.
"As part of its commitment to tackle ticket touting, the club has created a test purchase programme to help protect supporters from purchasing via unauthorised ticketing sites. The programme aims to identify and stop these sales.
"While selling or offering to sell tickets without the permission of the club is a criminal offence, LFC also intends to impose sanctions on any supporters found to be selling tickets through unofficial secondary ticketing sites.
"Sanctions could include ticket-buying suspensions and indefinite bans from Anfield. It could also mean that any tickets for the Champions League final in Madrid are invalid, and purchasers will be unable to gain access to Estadio Metropolitano."
Liverpool, meanwhile, have listened to requests from supporters by extending their season ticket renewal date for supporters who have purchased Champions League final tickets directly from the club.
Some Reds fans were concerned that the renewal date of Friday, May 24 gave them little time to also pay for their ticket for the showdown in Madrid.
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Now Liverpool have announced eligible supporters who are yet to renew now have until 3pm on Monday, June 3 to complete the renewal process.
The renewal date remains May 24 for all other season ticket holders, including those who have not purchased Champions League final tickets directly from the club.
