Trump sworn in as 45th US president with vow to 'put America first'
Donald Trump vowed to put "America first" as he set out a nationalist agenda after being sworn in as the 45th president of the United States.
President Trump's address broke with tradition as he sought to hammer home populist political points against globalisation and the Washington elite.
Promising to "rebuild our country and restore its promise for all of our people", he said: "From this day forward it is going to be only America first, America first."
Around 1.8 million people turned out for President Barack Obama's first inauguration in 2009, but photographs of the National Mall suggest considerably fewer travelled to Washington DC to see his successor sworn in at the Capitol building.
There were also ugly scenes on the streets nearby as thousands of anti-Trump protesters vented their anger.
Windows were damaged by people carrying metal poles and hammers, and police had to use hand-held water cannon, smoke grenades and tear gas to disperse the troublemakers, arresting around 100.
Other protests took place around the world as President Trump took the oath of office on the steps of the Capitol building just before noon local time (5pm GMT), his family and the outgoing president looking on.
Delivering his inaugural address, President Trump said: "Every decision on trade, on taxes, on immigration, on foreign affairs will be made to benefit American workers and American families.
"We must protect our borders from the ravages of other countries making our products, stealing our companies and destroying our jobs."
He added: "America will start winning again, winning like never before."
His pronouncements were met with raised eyebrows by some in the UK, with prominent Labour backbencher Chris Bryant calling it "the most embarrassingly vacuous speech I have ever heard" and labelling it "cod nationalism".
Other Labour MPs questioned how successful Britain's goal of a free trade deal with the US could now be, but Foreign Secretary Boris Johnson took a more conciliatory tone, tweeting his congratulations and adding: "Look forward to continuing strong UK - US bond."
Imploring the US to come together, President Trump said that a united America "is totally unstoppable".
Watched by his wife - and new First Lady - Melania, as well as Mr Obama and his wife Michelle, and former presidents George W Bush, Bill Clinton and Jimmy Carter, the new president said: "We are one nation, and their pain is our pain, their dreams are our dreams and their success will be our success. We share one heart, one home and one glorious destiny."
And as rain began to fall on the new president's shoulders, he added: "America will start winning again, winning like never before.
"We will bring back our jobs, we will bring back our borders, we will bring back our wealth and we will bring back our dreams."
President Trump said the US would "seek friendship and goodwill with the nations of the world" but with the understanding that it is the right of all countries to "put their own interests first".
"We do not seek to impose our way of life on anyone but rather to let it shine as an example. We will shine for everyone to follow," he said.
Hillary Clinton, who was defeated in a bitter presidential campaign that divided America, also attended the inauguration.
She appeared steely-eyed as she awaited Mr Trump's arrival ahead of the ceremony, but tweeted: "I'm here today to honor our democracy & its enduring values. I will never stop believing in our country & its future."
Mr Obama sent his own valedictory message to the American people, urging them to believe "not in my ability to bring about change, but in yours".
He tweeted: "It's been the honor of my life to serve you. You made me a better leader and a better man."
Despite suggesting he would start his work in earnest on Monday, President Trump wasted no time in settling himself into his new role.
He has already taken over Mr Obama's @POTUS Twitter handle, a stern-looking President Trump looking on, and his first Tweet a link to his inauguration speech on Facebook.
More importantly, policies from the new administration have already appeared on the White House website.
Confirming the fears of many environmentalists, President Trump underlined his intentions on climate change, saying he is "committed to eliminating harmful and unnecessary policies such as the Climate Action Plan and the Waters of the US rule".
He also said the US would be "committed to a foreign policy focused on American interests and American national security", vowing to pursue "joint and coalition military operations" to defeat so-called Islamic State and other radical Islamic terror groups.