Police have warned Ajax fans to beware of touts offering tickets for next Wednesday’s Champions League clash online for 100 times their cover price of €70.

The match against Tottenham Hotspur in the ArenA, Ajax’s first semi-final appearance in 22 years, is sold out but several online agencies are offering second-hand. Some fans have posted messages on auction sites offering to buy a place for as much as €8,500.

Police warned that tickets from unofficial sources may be forged or duplicated, with no prospect of a refund. Fans who do not have a valid ticket will not be allowed into the stadium. Details of official ticket sales are available on Ajax’s website.

‘People typically only discover a ticket is false when they are checked on entry to the stadium,’ said a police spokesman.

‘Preferably buy tickets at source, via the official website or official sales point of the event organisers,’ said Gijs van der Linden of the police National Online Fraud Helpline. ‘Buying tickets second hand is always risky. Only do so if you know and trust the seller.’

Ajax take a 1-0 lead into Wednesday night’s match after Donny van de Beek scored the only goal of the first leg in London. A win or draw will secure their place in the final, most likely against Barcelona, who beat Liverpool 3-0 in the first leg of the other semi-final.