An eyewitness said that cyclists were among those injured, while another said that the auto has been travelling "at speed - at least 50mph" when it appeared to "deliberately" crash into the barriers.
'I felt very shocked, ' he said.
"The auto went onto the wrong side of the road to where cyclists were waiting at lights and ploughed into them". Check back for the fullest version.
The Ford vehicle then continues towards College Green before pulling into a slip road and accelerating towards a security barrier outside Parliament. Then the police just jumped.
Armed officers from the Scotland Yard were at the scene instantly and one man has been arrested.
Sky News UK and other media outlets report there is a heavy armed police presence outside the building after the vehicle crash.
"There was smoke coming out of the auto", he added. I didn't see anyone else involved. "The guards started screaming to people to move away".
"It didn't look like an accident", he said.
The auto slammed into barriers that had been extended following the Westminster Bridge attack in March 2017 when Khalid Masood ploughed a vehicle into crowds on Westminster Bridge, killing four people. ISIS later claimed responsibility for the attack.
On June 19, 2017, a man drove a van into a crowd of worshippers leaving a mosque in north London, killing one man and injuring eight others.
"Considering recent events, I wanted to get out of the area". So I don't know why someone would drive into the barrier. None of the injuries was believed to be life-threatening, the police said in a tweet.
The Mayor of London, Sadiq Khan, praised first responders.
The incident sparked a huge security incident and several streets around the Palace of Westminster have been cordoned off.
Parliament is now on summer recess, and isn't due to reconvene until early September, meaning the Houses are fairly quiet at the moment.
This is a developing story.