At least seven people have died after three attackers drove a van into pedestrians and then jumped out and stated stabbing passers-by at Borough Market.
Armed police shot and killed three suspects, within eight minutes of the original incident, officers confirmed.
A witness named Eric claimed he saw a van driving on the wrong side of the road before three men jumped out and started running towards bars and restaurants, shouting “this is for Allah”.
Is London Bridge station open?
London Bridge, Borough and Bank stations were closed in the wake of the attack.
London Bridge and Borough stations remain closed, but Bank has now reopened.
London Bridge is on the Northern and Jubilee Underground lines as well connecting a number of National Rail services.
Borough is on the Northern Line.
Police have urged Londoners to avoid London Bridge and Borough Market
Express.co.uk heard from a witness that a white van had appeared to purposefully hit pedestrians on the bridge at 10.08pm.
Armed officers responded very quickly and bravely
Mark Rowley of Met Police
Metropolitan police are warning Londoners to avoid London Bridge and Borough Market.
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Mark Rowley, assistant commissioner for the Metropolitan police, said in statement: “You will understand that our knowledge of the incident is still growing but what we understand at the present time is:
“At 22:08hrs yesterday evening we began to receive reports that a vehicle had struck pedestrians on London Bridge.
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Emergency services still in the area following the London attack last night
“The suspects then left the vehicle and a number of people were stabbed, including an on-duty British Transport Police officer who was responding to the incident at London Bridge. He received serious but not life-threatening injuries. His family has been informed.
“Armed officers responded very quickly and bravely, confronting three male suspects who were shot and killed in Borough Market.
“The suspects had been confronted and shot by the police within eight minutes of the first call. The suspects were wearing what looked like explosive vests but these were later established to be hoaxes.
Met Police have confirmed that three suspects have been shot dead
“The ongoing operation is led by the Met, working closely with British Transport Police, City of London Police, the London Ambulance Service and the London Fire Brigade.
“At this stage, we believe that six people have died in addition to the three attackers shot dead by police. And at least 20 casualties have been taken to six hospitals across London.
“I'd like to repeat our request for the public to avoid the following areas: London Bridge and Borough Market. This is to allow emergency services to deal with this incident.”