Tom Elvidge, general manager of Uber Lonbdon, said: 'As soon as we heard about the incident we immediately suspended dynamic pricing all around the area of the attacks - and shortly afterwards across the whole of central London'.
Trump tweeted Monday morning that Khan had offered a "pathetic excuse" and "had to think fast on his "no reason to be alarmed" statement".
But the mayor was talking about the stepped-up police presence in the city after the attack - not about the attack itself.
On Saturday, at least seven people were killed by three masked men who drove a white van into pedestrians on the London Bridge, then leaped out and stabbed several people at Borough Market's nearby bars and restaurants.
The three men, wearing fake suicide bomb vests, were shot dead by eight officers outside a pub after police opened fire with an "unprecedented" hail of 50 bullets, while a bystander was also shot. May has been more measured, defending Mayor Sadiq Khan but not directly criticizing Trump.
Trump added that the media "is working hard to sell it!"
Khan, who belongs to the opposition Labour Party and is the first Muslim to be elected mayor of a major western European city, is popular in London and his response to Saturday's killings has been widely praised as dignified.
Asserting that Britain will continue to support military action to destroy ISIS in Iraq and Syria, she said, "working with other democratic governments we will agree ways to regulate cyberspace and prevent the spread of extremism and terrorist planning online".
She said, "I believe it is right that the United Kingdom is engaged in taking on and defeating groups like ISIS and their like around the world".
"Londoners will see an increased police presence today and over the course of the next few days. There is no reason to be alarmed by this".
Later Khan's spokesman said he was too busy to respond to Trump's "ill-informed" tweet. "The commissioner of the Metropolitan Police has said that the Met is well-resourced, and they are, and that they have very powerful counterterrorism capabilities and they do", May said. In a series of tweets, Trump said, "We need to be smart, vigilant and tough".
Debate in Britain grew, meanwhile, about the country's longstanding practice of most police officers going unarmed.
US President Donald Trump offered his help, tweeting "WE ARE WITH YOU".
The two men have history.
During a visit to Chicago in September a year ago, Khan endorsed Trump's opponent Hillary Clinton.
On Sunday Trump leveled an inaccurate criticism of London Mayor Sadiq Khan, saying the mayor was telling people there was "no reason to be alarmed" about the attack.
Londoners, even while mourning, expressed continuing determination to avoid giving in to the kind of fear the attackers had sought to sow.
London hospitals have also increased security, with patients attending Guy's or St Thomas' hospitals asked to bring photo ID with them to appointments.
Khan dismissed Trump Jr.'s comments at the time, saying he had been doing more important things in the wake of the Westminster attack than responding to tweets.