The chilling footage shows the grey Hyundai 4×4 mounting the pavement on the famous London bridge, striking a number of pedestrians before the woman is forced into the river.
The woman, whose identity remains unknown, was later pulled out of the Thames alive – although a spokesman for the Port of London Authority said she had sustained “serious” injuries.
The woman can be seen falling from the bridge in the shocking footage
It has not yet been confirmed if the woman jumped or was forced into the river by the speeding vehicle.
Police boats patrol the river in the aftermath of Wednesday's horrific events
He said: "I saw the car swerve to hit pedestrians, many of them were children.
"In a fit of panic people were jumping off the bridge and into the river, that was their only hope of survival."
On Wednesday evening, Scotland Yard's top anti-terror officer Mark Rowley confirmed that five people had been killed in the attack, including PC Keith Palmer.
London Terror Attack: LATEST PICTURES Thu, March 23, 2017
5 dead and 40 injured in Westminster terror attack
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Police forensic tent on Westminster Bridge
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He added that around 40 others have been injured.
Among the victims are five South Koreans, according to the foreign ministry in Seoul.
Three women and one man in their 50s and 60s suffered injuries including broken bones during the attack, while another woman in her 60s suffered a head injury while falling and is now in hospital receiving surgery.
The bridge was closed while authorities dealt with the incident
The seriousness of the injuries is not yet known but the five South Koreans are being treated in two London hospitals.
Meanwhile a spokesman confirmed three French schoolchildren were among those injured in the attack.
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He added that the three pupils are from the Saint-Joseph high school in Concarneau, Brittany.
French prime minister, Bernard Cazeneuve, tweeted: "Solidarity with our British friends struck terribly, full support to the injured French pupils, their families and their classmates."