At least 15 people were arrested after thousands of protesters took to the streets across the US to call on President Donald Trump to release his tax returns.

The arrests took place on Saturday in Berkeley, California, when fistfights broke out between supporters and opponents of the President, Efe news reported.

Two people were also injured in the fights.

Police fired tear gas to disperse the crowd and quell the fights, reporting that they had found some people in possession of prohibited items including a knife, helmets, clubs and a fake pistol.

Local authorities knew that there would be two demonstrations on Saturday both for and against Trump, while protests elsewhere in the country, however, were reported to be generally peaceful.

The "Tax March" movement had called for protests to begin at noon, coinciding with the day by which Americans traditionally must have filed their tax returns, though this year because April 15 fell on the weekend and Monday is a local holiday in Washington, taxpayers have until Tuesday, April 18, to file their returns.

The largest march took place in Washington, where protesters marched from the Capitol to the White House, but sizable anti- Trump demonstrations were also staged in Los Angeles, Chicago, Seattle and Austin, Texas.

In New York, hundreds of people carrying anti- Trump signs and effigies of the President gathered in downtown Bryant Park, from where they marched to Trump Tower.

Activists in Florida held dozens of marches around the state, in front of the condominiums at Trump Plaza in West Palm Beach and the entrance of his Mar-a-Lago mansion, where he is spending the weekend with his family.

The movement calls for "transparency" and complains in a statement on its Web site that "despite intense public pressure, President Trump has not yet done so (published his tax returns) - breaking with 40 years of precedent in the process."

The statement rejects the Trump government's excuse that "people don't care," and recalls an ABC/Washington Post survey that showed 74 per cent of Americans, including more than half of Republicans, want to know the president's tax history.

During Trump's presidential campaign, he kept postponing the release of his tax returns with the excuse that they were under audit.

Two days after he entered the White House, Presidential Adviser Kellyanne Conway said Trump was not going to disclose his tax situation because it became obvious during the campaign that US citizens really did not care about the matter.