A man wearing a suspected hoax explosive device knifed two people to death in a terror attack on Friday before being shot dead by police on London Bridge.
Three more people were injured in the stabbing spree which revived memories of a three-man attack on London Bridge two years ago that killed eight people.
Footage on Twitter filmed by eyewitnesses showed a scrum of people tackling the suspect on the ground before specialist armed officers arrived and fired as he made to get up.
London Mayor Sadiq Khan praised those onlookers who risked their own safety to try to disarm the suspect before the police arrived.
Police said they were called at 1:58pm (1358 GMT) and confronted the man by 2:03pm, shooting him dead.
The attack came a few hours before a number of people were wounded in a stabbing in one of the main shopping streets in the centre of the Dutch city of The Hague.
More From This Section
The two attacks happened on so-called "Black Friday", one of the busiest shopping days of the year in the run-up to Christmas, bringing more shoppers onto the streets.
The incident in London came less than two weeks before a general election at which Prime Minister Boris Johnson hopes to win a majority to enable him to take Britain out of the European Union.
The premier cut short a visit to his constituency to return to central London for a briefing by the police and a meeting of Britain's emergencies committee.
Johnson praised the emergency services and the public for their response, adding: "This country will never be cowed or divided or intimidated by this sort of attack."
"We retain an open mind as to any motive," he told reporters. "We believe a device that was strapped to the body of the suspect was a hoax explosive device."
"The guys that were there were just amazing. Absolutely incredible people. Heroes beyond belief."