Large protests against the Trump administration are taking place in cities across the US, marking the third iteration of No Kings rallies that have previously drawn crowds into the millions.

Organisers say they are protesting against policies imposed by US President Donald Trump, including the war in Iran, federal immigration enforcement and the rising cost of living.

Trump wants to rule over us as a tyrant. But this is America, and power belongs to the people - not to wannabe kings or their billionaire cronies, organisers said.

Trump allies have previously denounced the No Kings protests as the hate America rally and accused participants of being linked to the far-left Antifa movement.

Throughout the day on Saturday, demonstrations will take place in nearly every major US city, including New York, Washington DC, and Los Angeles. Rallies have already started in Washington DC and other cities, with throngs of people marching into the nation's capital from neighbouring Arlington, Virginia.

Like in previous iterations of No Kings, protestors hold up effigies of Trump, Vice President JD Vance and other officials in the administration, calling for their ousting and arrest.

The last No Kings rally in October drew crowds of nearly seven million people nationally. Several US states mobilised the National Guard, but organisers have maintained that the events are peaceful.

Since returning to the White House in January, Trump has expanded the scope of presidential power, using executive orders to dismantle parts of the federal government and deploying National Guard troops to US cities despite objections by state governors.

Earlier this year, federal immigration agents in Minneapolis shot and killed two US citizens, Alex Pretti and Renee Good, sparking outrage and nationwide protests. The president has also called on the administration's top law enforcement officials to prosecute his perceived political enemies.

The president says his actions are necessary to rebuild a country in crisis and has dismissed accusations that he is behaving like a dictator as hysterical. They're referring to me as a king. I'm not a king, he said in an interview with Fox News in October.

Critics warn some of the moves by his administration are unconstitutional and a threat to American democracy.

American expats abroad are also gathering to protest. Crowds have formed in Paris, London and Lisbon, where many hold signs calling the president a fascist and a war criminal, as well as calling for his impeachment and removal from office.