WASHINGTON - US President Donald Trump on Sunday issued a number of tweets in a bid to play down a number of protests across the country demanding the release of his tax returns.

"Someone should look into who paid for the small organized rallies yesterday," Trump tweeted on Sunday. "The election is over!"

Trump's remarks imply that he has no intention to issue his tax returns, some US media reports commented.

Demonstrators in dozens of US cities, including Washington, New York, Chicago and Palm Beach, where Trump was spending Easter weekend at his Mar-a-Lago resort, marched on Saturday to demand Trump release his tax returns. Some rallies were joined by thousands of people.

In Berkeley, California, police arrested at least 20 people at gatherings of about 200 pro-Trump and anti-Trump people in a park after fist fighting erupted. Officers confiscated knives and makeshift weapons.

During his campaign and after the election, the Trump camp repeatedly refused to release Trump's tax returns, saying they were under audit. However, tax experts said Trump is not barred from releasing the information during the audit.

While US presidents are not required to release their tax returns, nearly all US presidents had voluntarily released them since 1970s.

Shortly after Trump's inauguration in January, Kellyanne Conway, senior counselor to Trump, told US media that Trump would not release his tax returns, citing voters' indifference to the issue as one of the reasons.

However, multiple polls have found that the majority of US citizens want Trump to release his tax returns.

Comedy writer Frank Lesser, whose tweet in January sparked the idea for the Tax March, said the participation in the nationwide marches proves that people want to see Trump's returns.

"We march to demand that the president release his returns, as he has repeatedly promised, but failed, to do," the Tax March website reads. "We march because it is in the best interest of the American people to know what financial entanglements and conflicts of interest our leaders have."

A petition demanding Trump release his tax returns garnered more than 1 million signatures. Many lawmakers, including some Republicans, have also called on Trump to make them public.

The tax marches coincided with the April 18 deadline for tax returns.