Thousands of people took to the streets in European and Asian cities on Saturday, demonstrating in support of US protests against police brutality.
Police in the German city of Hamburg used pepper spray on protesters and were ready to deploy water cannons.
Several hundred "hooded and aggressive people" had put officers under pressure in the city centre, police said in a tweet, adding "We have already had to use pepper spray. With all due respect for emotions: attacks on police officers are unacceptable!"
At another location nearby, the authorities said some 350 people were standing in front of police water cannons and that officers were calling on loudspeakers for them to disperse.
One officer was injured, the police added.
The rolling, global protests reflect rising anger over police treatment of ethnic minorities, sparked by the May 25 killing of George Floyd in Minneapolis after a white officer detaining him knelt on his neck for nearly nine minutes as fellow officers stood by.
Europe has seen an unprecedented wave of anti-racism rallies drawing tens of thousands onto the streets.
In London, thousands of protesters ignored wet weather to crowd into Parliament Square, wearing face masks amid the coronavirus threat and waving placards and chanting: "No justice, no peace, no racist police."
Interior minister Priti Patel urged people not to protest in view of the pandemic, which has killed more people in Britain than anywhere in the world outside the United States
"I completely understand people's views and their desire for the right to protest but ... we are in a health pandemic across the United Kingdom," Patel told UK broadcasters. "I would say to those who want to protest - please don't."
In Paris the authorities banned demonstrations planned outside the US Embassy and on the lawns near the Eiffel Tower.
However, several hundred protesters, some holding "Black Lives Matters" signs, gathered on Place de la Concorde, close to the Embassy. Police had installed a long barrier across the square to prevent access to the embassy, which is also close to the Elysee presidential palace.
In Berlin, demonstrators filled the central Alexanderplatz, while there was also a protest in Warsaw.
PLACARDS AND FLAGS
In Brisbane, one of several Australian cities where rallies were held, police estimated 10,000 people joined a peaceful protest, wearing masks and holding "Black Lives Matter" placards. Many wrapped themselves in indigenous flags, calling for an end to police mistreatment of indigenous Australians.
Banners and slogans have focused not just on George Floyd but on a string of other controversies in specific countries as well as mistreatment of minorities in general.
In Sydney, a last-minute court decision overruled a coronavirus ban as several thousand people marched amid a heavy police presence.
In Tokyo, marchers protested against what they said was police mistreatment of a Kurdish man who says he was stopped while driving and shoved to the ground. Organisers said they were also marching in support of the Black Lives Matter movement.
"I want to show that there's racism in Japan now," said 17-year-old high school student Wakaba, who declined to give her family name.
In Seoul, dozens of South Korean activists and foreign residents gathered, some wearing black masks with "can't breathe" in Korean, echoing George Floyd's final words as he lay on the pavement.
With coronavirus pandemic restrictions in Bangkok, activists went online, asking for video and photos of people wearing black, raising their fists and holding signs, and explaining why they "stand united behind Black Lives Matter".
Protesters were expected to gather in Washington for a huge demonstration on Saturday as street marches across the United States entered a 12th day.