Seven people have been killed and at least 48 injured, 21 of whom are in a critical condition, in a terror attack on London Bridge late on Saturday evening.
A van hit pedestrians on the bridge before crashing by Borough Market at around 10pm. Three attackers left the vehicle and stabbed a number of people nearby, police have said.
Armed police shot dead the suspects who were wearing hoax explosive vests within eight minutes of the first call about the incident being received.
"We are treating this as a terrorist incident and a full investigation is already underway, led by the Met's Counter Terrorism Command," the Met Police said in a statement early on Sunday morning.
London Ambulance Service said more than 80 medics attended the scene in south London and the injured have been taken to several hospitals. NHS England has said that 21 of the injured are in a critical condition.
Met police assistant commissioner Mark Rowley has said one member of the public was injured by officers' gunshots as they stopped the attackers. Eight firearms officers fired an "unprecedented" 50 rounds during the attack.
Canadian Prime Minister Justin Trudeau has said a Canadian national is one of those killed. He said: "Canada strongly condemns the senseless attack that took place last night in London, United Kingdom, which killed and injured many innocent people. I am heartbroken that a Canadian is among those killed."
National General Election campaigning has been suspended by the major parties on Sunday, just four days before the country heads to the polls, and Prime Minister Theresa May has chaired an emergency Cobra meeting.
London mayor Sadiq Khan also attended. He said: “The Metropolitan Police are responding to the horrific terrorist attack at London Bridge and Borough Market. My thoughts are with everyone affected, and I'd like to thank the brave men and women of our emergency services who were first on the scene and will be working throughout the night.
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“I am in close contact with the Met Commissioner and senior officers and am being kept updated on all developments."
London Bridge and Borough stations remain closed and rail and Tube services are not calling at the stations. Rowley said cordons around the area "will have an impact on travel arrangements as we head into Monday morning" and has advised passengers to check with train and travel operators.
World leaders have reacted with support for the UK.
And in a strongly worded speech May warned that "enough is enough" and counter-terrorism measures must be reviewed, while internet companies must do more to tackle extremism.
Met police have made 12 arrests in raids in Barking in east London as part of their investigation.