Minneapolis, Minnesota - Massive protests against President Donald Trump kicked off Saturday across the US and beyond, as millions of people vent fury over what they see as his authoritarian bent and law-trampling governance.

It is the third time in less than a year that Americans have taken to the streets as part of a grassroots movement called "No Kings," the most vocal and visual conduit for opposition to Trump since he began his second term in January 2025.

Now they have something new to fume over – the war against Iran that Trump launched alongside Israel, with ever-shifting goals and timelines for completion.

US protests began in several cities, including Washington, Boston, and Atlanta, where thousands of people gathered in a park to decry authoritarianism.

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"No country can govern without the consent of the people," 36-year-old military veteran Marc McCaughey told AFP in Atlanta.

"We're out here because we feel that the Constitution is under threat in a multitude of different ways. Things aren't normal. They aren't okay."

In the Michigan town of West Bloomfield, near Detroit, people braved below-freezing temperatures to protest.

And in the capital, Washington, marchers – some carrying banners that blared "Trump Must Go Now!" and "Fight Fascism" – walked across a bridge over the Potomac River to the Lincoln Memorial, site of historic civil rights demonstrations of years past.

The anti-Trump mood has spilled beyond US borders, with rallies Saturday in European cities including Amsterdam, Madrid, and Rome, where 20,000 people marched under a heavy police presence.

"We don't want a world governed by kings... who make decisions from on high," said 29-year-old researcher Andrea Nossa.