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In Warsaw, Poland, law enforcement used tear gas on protesters, while police made arrests at a demonstration in London's Hyde Park.
Police in several German cities enforced distancing rules as thousands of people gathered to vent anger over economies in freefall and perceived losses of freedom.
Police in Stuttgart said that the number of demonstrators exceeded the permitted threshold of 5,000; they directed other protesters to another open space. Police said they were enforcing a mask requirement under threat of a 300-euro ($325) fine.
The permitted number of 1,000 protesters also was reached in Munich at the site of the now-canceled Oktoberfest beer festival. It was one of a number of gatherings across the southern state of Bavaria.
Dozens of people, including a senator, were detained during a protest by business owners in the Polish capital against coronavirus restrictions, while police used tear gas against protesters. Warsaw officials said the gathering was illegal because they had not approved it
In Britain, anti-lockdown and anti-vaccine protesters held a gathering in Hyde Park in central London and were met by a heavy police presence.
The protesters chanted "Freedom" and held handmade signs. Some sat on the grass and had picnics while observing social-distancing guidelines while others ignored the rules and gathered in groups.
Officers tried to disperse the groups, threatening them with fines if they didn't comply. They arrested 13 people, the London Metropolitan Police Service said.
The protests came as multiple European cities have started to loosen some of the restrictions on movement, gatherings and business operations.
The Associated Press contributed to this report.