Celtic fans arrested as Amsterdam clashes leave eight police injured Eight officers were injured as fans clashed in Amsterdam before Celtic's champions league match with Ajax. Police said supporters armed with bottles and sticks fought in Dam Square on Wednesday afternoon. A spokesman said the majority of the 15 arrested were Celtic fans. "At the end of the afternoon a large group of Celtic supporters attacked police officers in plain clothes," a police spokesman told the Press Association. Eight were injured and one was knocked unconscious. A few of them had broken noses and needed stitches above their eyebrows and on their lips. Bottles and sticks were used in the attack which came out of nowhere. There were 15 arrests, mostly Celtic supporters. "The officers took quite a beating," police spokesman Rob van der Veen told Reuters. One of the officers was unconscious, another had his nose broken. Amsterdam police said it expected the number of 15 arrests to rise and that a final figures would be "high." It is thought that fans from other European clubs were involved. News portal nu.nl reported that fans of Belgian club Anderlecht and Germany's St Pauli were also in the city. Large numbers of Dinamo Zagreb fans are also in Amsterdam before Thursday's Europa League match against Dutch club PSV Eindhoven. The incidents came the day after a group of Celtic fans were attacked by masked Dutch fans in an Amsterdam bar. It follows on from trouble involving Ajax fans in the first game between the teams in Glasgow two weeks ago. Celtic supporters had earlier been urged by the club to be careful. A statement on the Celtic website said: "Celtic Football Club is urging all supporters in Amsterdam for tonight's UEFA Champions League tie with Ajax to be extra vigilant following an unprovoked attack on Celtic fans last night Celtic are urging all supporters to be extra vigilant in the city centre and at the Amsterdam ArenA, and to only stick to the advised areas for safety reasons.