Dutch police said that they had arrested 76 Ajax supporters suspected of seeking a confrontation with Manchester United supporters the night before the clubs meet in the Europa League.
Police said on Thursday that the men were detained a day earlier under heightened security rules imposed by Amsterdam's mayor. Spokesman Ad Smit said the men were found to have a pair of brass knuckles, tear gas, a club "and a large amount of narcotics."
They were held overnight and will face varying fines of up to $780.
Another 54 supporters of Belgian club Anderlecht, who were also thought to be seeking confrontation with United supporters, were detained and sent home. On Wednesday, 12 people were arrested for "football-related incidents."