Dozens of people were hurt as German police and anti-capitalist demonstrators clashed Thursday in Hamburg during a march protesting the upcoming Group of 20 summit.
Thousands of people are taking part in protests against the G-20 economic summit, which will be held Friday and Saturday.
Watch: After Warm Welcome in Poland, Trump Arrives in Less-friendly Hamburg
As U.S. President Donald Trump met with German Chancellor Angela Merkel on Thursday afternoon, thousands of protesters gathered in the historic Hamburg Fish Market and confronted police, some tossing bottles. Police responded with water cannons, pepper spray and batons.
Nearly 75 police officers were injured throughout the evening, with three requiring treatment at a hospital, police said. The pilots of a police helicopter sustained eye injuries when laser pointers were directed at them, police said.
Medics were also seen assisting injured protesters on the sidelines of the march.
Video footage showed masked protesters blocking streets with construction material and setting small fires. Local media reported some property damage, including burning cars and smashed shop windows.
Hamburg police also tweeted that the protesters were throwing "bottles and objects" at them.
In all, more than 100,000 protesters are expected in Hamburg for the summit, with some 8,000 considered part of Europe's violent left-wing scene, according to police.
The northern port city has boosted its police with reinforcements from around the country and has 20,000 officers on hand to patrol Hamburg's streets, skies and waterways.
After the rousing welcome Trump got in Poland, he arrived in less friendly territory in Hamburg to face tough issues of trade and climate, as well as his first face-to-face meeting with Russian President Vladimir Putin.
Protesters had been camping out since the start of the week, waiting for the U.S. leader.
"What are my thoughts about it? Oh, Donald Trump is kind of really symbolic for this issue, how to manage the crisis in the world," said Alma Wunder, a demonstrator. "He is kind of the symbol [of] our enemies."
WATCH: German police use water cannons on anti-capitalist protesters in Hamburg
Hamburg has historically been a hotbed of left-wing, anti-capitalist protests — a symbol of openness that Merkel wants to showcase as she makes her case against protectionism.
"I think we're united in our will to strengthen multilateral relations at the G-20 summit, that we need an open society, especially open trade flows," Merkel said during a news conference before Trump's arrival.