Police have confirmed they are responding to three separate incidents along the Thames River.
One person has been killed at London Bridge - and one of the casualties is reportedly a police officer.
The Sun newspaper is reporting that two attackers have been shot dead by police near London Bridge.
Soon after, reports came in of stabbings around Borough Market, just steps away from the bridge.
At 2:25 a.m., police announced the two incidents at London Bridge and Borough Market were "terrorist incidents". The Vauxhall stabbing is not connect to the incidents, they tweeted.
British Prime Minister Theresa May says the incidents involving a vehicle and reported stabbings in London "is being treated as a potential act of terrorism". A security officer near London Bridge also told the network she saw people bloodied, running and screaming from the scene.
"Whatever the United States can do to help out in London and the U.K., we will be there", he tweeted.
News reports that London Bridge has been closed as armed police gather.
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The attack comes less than three months after an attacker ran down people with a vehicle on Westminster Bridge, killing four, then stabbed a policeman to death outside Parliament.
Some netizens witnessed the incident tweeted that they saw people got injured and the police has come to deal with it. I was in the back of an Uber cab driving south over London Bridge.
BBC reporter, Holly Jones, was at the scene as events unfolded and described witnessing a white van travelling "at about 50 miles an hour".
Three incidents are now being reported from London.
The police department said there also was a stabbing at another location, the Vauxhall district southwest of London Bridge, but it was unrelated to the first two attacks.
Eyewitnesses reported panic in the vicinity of the attacks, close to a major transport hub and in an area packed with restaurants and bars.
She said that among the injured was a French woman who told her she did not know where the two people who had been with her were.
Jamie, who was in a restaurant on Rochester Walk near London Bridge, said customers ran to hide after hearing a "massive bang" and seeing intruders rush in.