'Flash bang' grenades were thrown into rioting crowds as outnumbered police officers tried to bring order to the streets close to the Capitol.
Tear gas was thrown at protestors as police chased them through the streets of Washington, just one hour before official proceedings began.
But hours after the ceremony, violence continued.
Chaos erupted downtown in the city as miles from the suits and ties in the Capitol, hooded men and women are marching, throwing over bins, smashing windows and spray-painting buildings.
Police chased them with batons forcing the crowd to disperse across the streets.
Those caught were were doused with pepper spray.
As scenes became increasingly out of control units from the US army were called in.
Those on the streets have said they are in the middle of a "riot".
Shop windows smashed by rioters in Washington
Two police officers have been hospitalised and at least 250 protesters arrested in the shocking scenes which have unfolded across Washington.
The DC law enforcers were injured in run-ins with protesters, DC Fire Spokesman Vito Maggiolo told CNN.
Rocks were thrown at officers and cars set on fire for hours after the inauguration took place.
Images of smashed shop fronts and car windows have appeared on social media.
Trump has been inaugurated as the 45th President of the United States in a grand ceremony in Washington DC.
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Trump's 35-word swearing-in took place on a 10,000 square foot specially-built platform in front of the Capitol that holds 1,600 people.
Outside the White House counter protest groups condemned or celebrated the billionaire businessman becoming president of the United States.
Shocking images of cars set on fire in Washington have been shown on TV
Windows shattered as anti-Trump protesters cause mayhem and leave customers hiding under tables
More than 90 people were arrested around the inauguration
Washington streets in chaotic scenes as police chase protesters with grenades
On Thursday evening, protesters clashed with police outside a pro-Donald Trump black tie event, called the 'DeploraBall'.
Footage posted on social media appeared to show police in riot gear using pepper spray and tear gas to disperse the protesters.
He will be being watched by thousands of security officials, police, FBI agents and will be being covered by snipers.
Police on the streets are swarming around protestors after some turned violent
Smoke fills the air after police threw 'flash bang' grenades into crowds for calm
PROTESTS at Trump's Inauguration Day
Fri, January 20, 2017
Protestors were chased through the streets of Washington as violent scenes broke out close to the Donald Trump inauguration in Washington.
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Police and demonstrators clash in downtown Washington after a limo was set on fire.
Uniformed officers have lined the streets in a bid to keep the crowds calm, while support in full riot gear wait behind them.
Earlier reports suggested there will be snipers waiting on roofs above Washington and scene kilometres around the White House blocked to cars.
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Obama and Trump leave the Whitehouse together
Hilary and Bill Clinton attend Trump's inauguration
Donald Trump will be inaugurated as the 45th president of the US with wife Melania by his side
Crowds gathered in Washington are being watched over by thousands of police and security
Trump supporters stand along Pennsylvania Avenue for the singing of the national anthem
Firefighters run to extinguish a burning vehicle
Dump trucks carrying sand have also been brought in to block streets.
At one checkpoint, Black Lives Matter protesters were chanting “Shut it down” before five men chained themselves together, preventing anyone from passing.
Trump supporters who have "lost friends" since visiting the ballot box said they were happy to be able to mix with others who believe in the new president.
Mr Trump has been criticised for stoking racial tensions in his bid for the presidency.
Demonstrators lit fires in the streets.
Protestors reportedly outnumbered supporters at Mr Trump's inauguration.
Demonstrators lit fires in the streets of Washington as officers tried to contain the situation.
The president came under fire for stoking racial tensions during his election campaign.
One protestor carried a placard that read: "Make racists scared again."