Protests erupt ahead of G20 summit in Hamburg (TRUMP BRINGS ECHOES OF '99)

The skirmish followed an hour-long standoff on a street that runs alongside Hamburg's downtown harbor. Thousands of protesters were gathered, and some began lobbing glass bottles and other objects as police rushed a group of "black bloc" activists huddled in the middle of the street. They were dressed in dark clothes with their faces concealed and carried signs condemning the state and promising, "Welcome to hell."

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The street marches and rallies planned for the summit -- like at past G-2 gatherings -- cover a range of issues including calls for environmental protections, denunciations of ethnic nationalism and opposition to free trade. But the Hamburg protests have gained added momentum as a stand against President Trump and his brand of "America First" populism. An estimated 100,000 protesters were expected to converge on the old merchant city during the G-20 summit, which begins Friday.

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Authorities mounted the largest police operation in the city's history. At least 20,000 officers were being deployed at about 30 registered demonstrations. Forty-five water cannons were on hand to disperse crowds. Some were used Tuesday evening to clear the streets of early protesters.