Liverpool say they could impose Anfield bans on any supporters found to be selling Champions League final tickets for marked up prices online.
Jurgen Klopp's side face Tottenham in European football's showpiece event at the Wanda Metropolitano in Madrid on June 1, which has led to a scramble for match tickets from both sets of supporters.
UEFA have allocated just over 50 per cent of the tickets to fans, which led to Liverpool and Tottenham supporters' trusts urging sponsors to return theirs.
Tickets on resale sites online are selling for up to €40,000 (£35,000) and Liverpool have released a statement reminding supporters over potentially fake tickets and warning them anyone caught trying to make profits on secondary and unofficial ticketing sites will face sanctions.
"Fans are warned that buying tickets via unofficial online sources does not guarantee tickets are genuine or that they will actually receive them," the statement said.
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"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."