Manchester derby: Tickets for sale at more than £2,200
Tickets for the sell-out Manchester derby at the Etihad Stadium have been offered at 40 times the asking price.
Manchester City are due to play Manchester United in the potential Premier League title decider later.
Tickets are being put for sale online at about £2,200 - more than the cost of three season tickets.
Police have urged fans not to buy tickets from unofficial sources and say any fans in the opposing team's section will be ejected.
About 47,000 fans are expected to watch the match at the stadium and thousands more will be watching in pubs.
Ch Supt John O'Hare said: "I would urge fans to think twice before buying tickets from unofficial sources because there will be people attempting to profit from this game, either by selling tickets at hugely inflated prices or by selling fake or non-existent tickets."
He added: "It is inevitable some fans will be left disappointed at not being able to attend the match, but that is better than paying hundreds or thousands for a ticket only to get turned away at a turnstile."
One website has offered pairs of tickets for city fans at £4,512.98 compared to the most expensive match day ticket at £52 with the highest price a fan can pay for a hospitality ticket valued at £400.
John Paul O'Neil, of fanzine Red Issue, said individual fans had been offered up to £600 for a ticket.
Extra police will patrol the city centre and officers will be visiting pubs where the match is being shown live on TV.
Ch Supt O'Hare said: "We want fans to enjoy themselves, but at the same time, we want to make it clear to the minority who may be thinking of causing any trouble that we will clamp down hard on them.
"We want to ensure that the city of Manchester, both of its clubs and its fans are remembered for the right reasons."
Police have warned anyone caught with alcohol on the streets within an exclusion zone, stretching from the city centre to the stadium, will have it confiscated.
Anyone arriving at the stadium under the influence of excess alcohol will also be refused entry, the force said.