Czech police have drafted in an extra 250 officers ahead of the Europa Conference League final between West Ham and Fiorentina in Prague.
Local police are working in conjunction with state police and UEFA to ensure the match passes off peacefully.
However, one officer told the PA news agency there had already been “a couple of incidents” involving West Ham fans, and added that they are “prepared for trouble”.
Around 20,000 Hammers fans are expected to travel to the Czech capital, but the majority are without tickets as both clubs only have an allocation of less than 5,000 each for the match.
Thousands had already arrived in Prague by Tuesday afternoon, the day before the final.
Fan parks will be set up in the city centre so those supporters without tickets can watch the match on a big screen.
A shuttle bus service has also been arranged to ferry fans straight from the airport to the parks.
West Ham’s semi-final victory at AZ Alkmaar was marred by a large group of Dutch fans attempting to storm a section full of the friends and family of West Ham’s players and staff.
Wednesday’s final is West Ham’s first in Europe since 1976, and they are bidding to win a first trophy since the FA Cup 43 years ago.
