German police shot a man armed with a small axe and a firebomb near Hamburg's Reeperbahn, the heavily touristed street in the heart of the northern port city's nightlife district.
The man was hit in the leg by an officer on Sunday afternoon and is now receiving medical treatment, a police spokesman said.
The incident raised major alarm as Hamburg is one of 10 German cities hosting Euro 2024 matches. Poland squares off there against the Netherlands on Sunday.
But a police spokesman said that early indications suggested "no football connection" and that the man acted alone.
The police operation was just a short walk away from the city's official fan zone. Police said football fans there were "well-protected" and never in danger.
Tens of thousands of Dutch supporters earlier marched down the streets of the St Pauli nightlife district, where the Reeperbahn is located.
According to police, the man had come out of a pub on a street adjacent to the Reeperbahn with what was described as a pickaxe.
He waved the tool at police officers in a "threatening manner," according to the spokesman's account. He was also carrying a Molotov cocktail.
Police asked him to put down the axe. When he refused after several warnings, the officers opened fire and shot him in the leg.
