Islamic State group claimed responsibility for London attacks, an online news agency affiliated with them said
UK Prime Minister Theresa May said on Sunday that Britain's controversial counter-terrorism strategy must be reviewed, after attackers killed seven people the previous night in a vehicular and stabbing attack.
London's Metropolitan Police arrested 12 people in the Barking district of east London in connection with the attack and raids were continuing there, the force said.
The Islamic State (IS) group claimed responsibility for the attacks, an online news agency affiliated with the militants said. "A security detachment from Islamic state carried out London attacks yesterday," the Aamaq news agency said.
Late on Saturday evening, attackers drove a van at high speed into pedestrians on London Bridge before stabbing revellers on the street and in nearby bars, killing at least seven people and wounding more than 48.
Armed police rushed to the scene and shot dead three male suspects in the Borough Market area just south of the bridge in central London, as authorities urged Londoners on Twitter to "run, hide, tell" if they were caught up in the violence.
British Transport Police confirmed that one of its officers were stabbed in the face while trying to help victims in the Borough Market area. Metropolitan Police Commissioner Cressida Dick said on Sunday morning that the death toll had risen to seven, revising an earlier death toll of six.
The attacks come days ahead of an 8 June election and less than two weeks after a suicide bomber killed 22 people at a pop concert by US singer Ariana Grande in Manchester in northern England. There was no immediate claim of responsibility.
We are all shocked and angry today - but this is our city. We will never let these cowards win and we will never be cowed by terrorism. pic.twitter.com/kcosumkdCR
— Sadiq Khan (@SadiqKhan) June 4, 2017
Leaders of Britain's major political parties have all issued messages of condolences to the victims of the terror attack and suspended their election campaigning till this evening.
Speaking on Sunday morning, May said the attack was not connected with the Manchester suicide attack that took place two weeks ago.
General election to go ahead
She also said that the UK general election will not be postponed and called on allied governments to work with Britain to "regulate cyberspace to prevent the spread of extremism".
"We need to review Britain's counter-terrorism strategy to make sure the police and security services have all the powers they need and if we need to increase the length of custodial sentences for terrorism-related offences, even apparently less serious offences, that is what we will do," May told journalists outside Downing Street.
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Mark Rowley, Britain's top anti-terrorism officer, said the three attackers had been wearing what looked like explosive vests that were later found to have been hoaxes.
The BBC showed a photograph of two possible London attackers shot by police, one of whom had canisters strapped to his body. Hours after the attack the area remained sealed off and patrolled by armed police and counter-terrorism officers.
The London ambulance service said more than 48 people had been taken to hospitals across the city.
A Reuters reporter said sometime after the attack began that he had heard loud bangs near the Borough Market area, but these appeared to be controlled explosions by security services.
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.
Witnesses described a white van careering into pedestrians near London Bridge and knocking over several people.
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"It looked like he was aiming for groups of people. I froze because I didn't know what to do," Mark Roberts, 53, a management consultant, told Reuters. He saw at least six people on the ground after the van veered on and off the pavement.
"It was horrendous," he said.
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".
Witnesses said people ran into a bar to seek shelter.
"People started running and screaming, and the van crashes into the railing behind. We went towards Borough Market and everyone went inside [the bar]. Everyone in the bar started pushing people from the exits," one witness who gave his name as Brian, 32, told Reuters.
Another witness, who declined to be named, his white top covered in blood, described a scene of panic in the bar.
"They hit the emergency alarm. There was a line of people going down to the emergency exit. And then people started screaming coming back up," the 31-year-old said.
"Around the corner there was a guy with a stab wound on his neck ... There was a doctor in the pub and she helped him. They put pressure on the stab wound."
Brutal and shocking incidents reported in London. My thoughts are with the victims and their families. Thank you to the emergency services.
— Jeremy Corbyn (@jeremycorbyn) June 3, 2017
BBC radio said witnesses saw people throwing tables and chairs at the perpetrators of the attack to protect themselves.
The BBC showed dozens of people, evidently caught up in the attack, being escorted through a police cordon with their hands on their heads.
The Islamic State group, losing territory in Syria and Iraq to an advance backed by a US-led coalition, sent out a call on instant messaging service Telegram early on Saturday urging its followers to launch attacks with trucks, knives and guns against "crusaders" during the Muslim holy month of Ramadan.
Similar attacks, in Berlin, Nice, Brussels and Paris, have been carried out by militants over the past two years.
"Following updates from police and security officials, I can confirm that the terrible incident in London is being treated as a potential act of terrorism," Prime Minister Theresa May said.
London's Thames river police said they worked with the lifeboat rescue service to help evacuate people caught up in the attack, described by police as a terrorist incident.
Trump brings up Muslim ban
US President Donald Trump took to Twitter to bring up his Muslim ban, which is being held up by the courts, just after news of the attack first broke.
"We need to be smart, vigilant and tough. We need the courts to give us back our rights. We need the Travel Ban as an extra level of safety!" he tweeted.
The President of the US has exploited an ongoing tragedy in London for his ends; rethink urgently needed on his forthcoming State visit. https://t.co/uWJLLDYjMm
— Larry the Cat (@Number10cat) June 3, 2017
He then offered to help Britain. The White House said he had been briefed on the incidents by his national security team.
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.
"We were in an Uber [taxi] going towards London Bridge and suddenly we saw people running. The Uber stopped, we asked people what was going on – people said there was shooting," said Yoann Belmere, 40, a French banker living in London.
"Now the area is completely closed with police cars going one way and ambulances going the other," he told Reuters.
A witness told CNN two men had entered a restaurant in the Borough Market area and stabbed two people inside. He said a waitress was stabbed in the throat and a man was stabbed in the back.
The Manchester bombing on 22 May 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.