US PRESIDENT Donald Trump has unleashed on protesters, mocking millions who took part in marches across the globe.

Just hours into his new position, Mr Trump touched off a stormy debate over the extent of his popular support, even before taking his first concrete actions in office.

The new president turned to Twitter and took a swipe at celebrities, asking why they didn’t use their star power at the ballot box.

Watched protests yesterday but was under the impression that we just had an election! Why didn't these people vote? Celebs hurt cause badly. — Donald J. Trump (@realDonaldTrump) January 22, 2017

Mr Trump’s tweet was referring to the actors, singers, writers and filmmakers who took the stage at the Washington march to speak against the new president.

An hour later he adopted a more conciliatory tone, and tweeted that “peaceful protests are a hallmark of our democracy”.

Peaceful protests are a hallmark of our democracy. Even if I don't always agree, I recognize the rights of people to express their views. — Donald J. Trump (@realDonaldTrump) January 22, 2017

More than two million people are estimated to have taken part in the women-led marches organised in the United States and around the world to defend women’s rights and oppose an array of policy stances from the new president.

His attack comes after Mr Trump faced unfavourable comparisons to the turnout for his inauguration a day earlier when he launched a sharp attack on the media, saying they lied about the numbers watching his swearing-in.

Mr Trump tweeted that millions more watched his inauguration compared to Barack Obama’s four years ago.

Wow, television ratings just out: 31 million people watched the Inauguration, 11 million more than the very good ratings from 4 years ago! — Donald J. Trump (@realDonaldTrump) January 22, 2017

He also insisted Washington was packed for his big day.

“It looked like a million, million and a half people,” he said, adding that “all the way back to the Washington Monument was packed.”

The Capitol, where Trump took the oath of office, is just two kilometres from the monument.

White House press secretary Sean Spicer also lashed out at media that published photos demonstrating that the crowd was far from reaching the monument — calling their reporting “shameful”.

TRUMP’S NUMBER OBSESSION

Burned by past controversies over the size of demonstrations, US capital authorities no longer estimate crowd sizes.

The sizes can, however, be compared through analysis of aerial photos, and those — backed by numbers from the transit authority about Metro usage — showed beyond doubt that the crowd at Trump’s inauguration was far smaller than when Barack Obama took office in 2009.

“In the big scheme of things, the size of the crowd is a small matter,” tweeted former Obama adviser David Axelrod.

“The fact that the (president) is so obsessed by it is not.”

The Trump team appeared on the defensive on Sunday when asked on television about the administration’s preoccupation with crowd size.

When senior aide Kellyanne Conway was asked on NBC why Mr Trump sent out his spokesman to convey a “provable falsehood” about the turnout, she replied that “Sean Spicer gave alternative facts”.

That statement caused a huge response on Twitter, with mocking comments about #alternativefacts trending to the top in the US and to the second-highest spot worldwide.

Both Ms Conway and Mr Spicer sought on Sunday to shift the debate to the days ahead.

They noted that the Republican president had a hectic schedule for the week, including plans to sign several executive orders to carry out campaign promises.

On Thursday, he will take part in a meeting of Republican members of Congress in Philadelphia.

And on Friday he is to host British prime minister Theresa May — the first White House visit of a foreign leader under the new administration.

“The two of them came in, similarly, through Brexit and through this movement here in the United States,” Ms Conway said on ABC, referring to the surprise vote in Britain to leave the European Union.

“They’re going to help renegotiate US and UK trade,” she said on NBC.

A few days before taking the oath of office, Mr Trump predicted that Brexit would be “a success” and announced that he wanted to quickly sign a trade agreement with Britain.

TILLERSON GETS KEY SUPPORT

With only two of his cabinet nominees confirmed so far by the Senate, Mr Trump received a bit of good news on Sunday about his pick to head the powerful State Department, former ExxonMobil chief Rex Tillerson.

Two leading Republican senators, Lindsey Graham and John McCain — both of whom had expressed reservations about Tillerson — said they would back his nomination.

Meanwhile, the Justice Department said that government anti-nepotism laws would not prevent Mr Trump’s son-in-law, Jared Kushner, from serving as a top adviser to the new president.

Separately, a petition on the Whitehouse.gov site demanding that the billionaire president immediately release his tax returns passed 100,000 signatures, the threshold at which the White House is supposed to respond within 30 days.

But Mr Trump’s advisers rather abruptly closed the door on that possibility — despite his repeated campaign promises to release the returns once a federal tax audit was completed.

“He’s not going to release his tax returns,” Ms Conway said flatly on ABC.

“We litigated this all through the election. People didn’t care, they voted for him.”

Mr Trump was the first major White House candidate in decades to refuse to release his returns.

He has assumed the presidency with the lowest popularity ratings of any president in 40 years, according to several recent polls.

— with staff writers