Within hours, May was in front of the cameras, telling the nation in a speech broadcast via BBC on Sunday, "It is time to say, 'Enough is enough'".
She said the series of attacks were not connected in terms of planning and execution, but were inspired by what she called a "single, evil ideology of Islamist extremism" that represented a perversion of Islam and of the truth.
Trump also spoke with British Prime Minister Theresa May to offer condolences and offered Washington's "full support" in investigating and bringing the perpetrators to justice, the White House said in a statement.
Renan Marquese, a sous-chef at a tapas restaurant, said he was working when he heard chaotic sounds outside.
The three assailants were shot dead within eight minutes of police receiving the first emergency call. The arrests followed a raid by police at a flat owned by one of the three attackers. More homes in the area were being searched. From the window, I could see an injured person being treated by emergency personnel.
Rowley lauded the courage of officers who ran toward the attack as it unfolded.
"The bravery he showed was outstanding and makes me extremely proud", Crowther said.
Thirty-six victims are still in hospitals and 21 of them are in critical condition, the National Health Service said Sunday.
London Mayor Sadiq Khan praised the quick response from law enforcement.
"Over the next few days, Londoners and visitors will be seeing an increased police presence".
In another tweet, Trump derided gun control advocates.
"We believe three people were involved, but we still have got some more inquiries to do to be 100 percent confident in that", he said.
Tory campaign guru Jim Messina who helped mastermind Barack Obama’s victories challenged You Gov general manager Ben Leet to a bet over the prediction
On Saturday night, following the attack, Mr Trump tweeted a message of support to the United Kingdom, but also sparked controversy after he called for his travel ban on visitors from six predominantly Muslim countries to be upheld by U.S. courts.
The spokesman also accused Trump of "deliberately" taking Khan's words out of context.
Warner said Trump has had more than 90 days to review the procedures for admitting people from certain countries. Canadians stand united with the British people. K., we will be there - WE ARE WITH YOU.
Chris Jacobs, 52, and his wife, Kavita Jacobs, 49, were woken by police officers banging on their door on the third floor of an apartment building at Borough Market.
"It was horrific", he said.
He joined a stream of people coming out of a nearby restaurant and was told to run across London Bridge. The trio wore apparent suicide belts that were later revealed to be fakes.
MR GERARD VOWLS, 47, on seeing a woman being stabbed 10 or 15 times by three men. "It could have happened to me too". Among the wounded were German, French and Spanish citizens, officials said. A dozen people were arrested, police said.
After the Manchester attack, most analysts said that May was the politician most likely to benefit, because she is the incumbent leader and security is usually seen as a Conservative strength.
It was in the market, just south of the bridge, where police killed the attackers and ended the rampage.
She said her brother survived because the attackers missed all his vital organs. Police later said Masood had no links to extremist groups such as ISIS or al-Qaeda. Some 22 people were also killed last month in a suicide bombing at an Ariana Grande concert in Manchester. ISIS claimed responsibility but that claim can not be verified.
Mrs May set out a four-pronged strategy to tackle terror by countering radical ideology; clamping down on online extremism; preventing the growth of segregated communities; and giving extra powers to police, security agencies and courts.
European Commission chief Jean-Claude Juncker, in letter to British Prime Minister Theresa May: "I know that the people of London will carry on defiantly, just like the people of Manchester showed us such a short time ago".