Suspected militants drove a van into pedestrians at high speed on London Bridge on Saturday night before stabbing revellers on streets nearby Borough Market, killing seven people and wounding close to 50.
Armed police rushed to the scene and shot dead the three male attackers in the Borough Market area near the bridge, as authorities urged Londoners on Twitter to "run, hide, tell" if they were caught up in the violence.
The attacks came just five days ahead of a national parliamentary election on Thursday. The ruling Conservative Party suspended national campaigning on Sunday, a spokesman for Prime Minister Theresa May said.
The killings also occurred less than two weeks after a suicide bomber killed 22 people at a pop concert by U.S. singer Ariana Grande in Manchester in northern England.
There was no immediate claim of responsibility.
The London Ambulance Service said 48 people had been taken to five hospitals across the city and a number of others had been treated at the scene for minor injuries.
London Mayor Sadiq Khan spoke of a "cowardly attack on innocent Londoners and visitors to our city enjoying their Saturday night".
British Prime Minister Theresa May today called the attacks at the iconic London Bridge and Borough market here as "terrible" and a "potential act of terrorism". (Text: Agencies)
Emergency personnel tend to wounded on London Bridge on Saturday. Metropolitan Police Service Assistant Commissioner Mark Rowley (not in picture) said “At 22:08hrs yesterday [June 3] evening we began to receive reports that a vehicle had struck pedestrians on London Bridge.”
People are lead to safety on Southwark Bridge away from London Bridge after the attack. After mowing down pedestrians, the van drove from London Bridge to Borough Market.
In this image made from PA Video footage, people receive medical attention in Thrale Street near London Bridge. Streets around London Bridge and Borough Market, fashionable districts packed with bars and restaurants, would have been busy with people on a Saturday night out.
Police officers clear the area near Borough market at London Bridge. A taxi driver told the BBC that three men got out of the van with long knives and "went randomly along Borough High Street stabbing people."
Counter-terrorism special forces are seen at London Bridge late on Saturday night.
Armed police officers patrol in Borough Market, in London on Sunday. Police rushed to the scene and shot dead the three male attackers in the area near the bridge.
This photo taken by photographer Gabriele Sciotto shows a man, foreground, one of the suspects, wearing what appear to be canisters strapped to his chest lying on the ground after being shot by police outside Borough Market in London on June 3, 2017.
Authorities urged Londoners on Twitter to "run, hide, tell" if they were caught up in the violence. In this picture police officers with riot shields are seen on Borough High Street after the terror attack.
Guests from the Premier Inn Bankside Hotel are evacuated and kept in a group with police on Upper Thames Street. The BBC showed dozens of people, evidently caught up in the attack, being escorted to safety through a police cordon with their hands on their heads.
Similar attacks, in Berlin, Nice, Brussels and Paris, have been carried out by militants over the past two years. In this picture police respond to reports of a van hitting pedestrians on London Bridge in central London.
A police officer clears people away from the area near London Bridge. The incident bore similarities to a March attack on Westminster Bridge, west of London Bridge, in which a man killed five people after driving into a crowd of pedestrians before stabbing a police officer in the grounds of parliament.
People run down Borough High Street as police deal with the terror incident at London Bridge. The Manchester bombing on May 22 was the deadliest attack in Britain since July 2005, when four British Muslim suicide bombers killed 52 people in coordinated attacks on London's transport network.