British police arrested 12 people Sunday in connection with the attacks in London that left seven people dead, after raiding several addresses in Barking, a suburb to the east of the capital.
He said he believed there were more than three attackers. Highlighting that this was the third terror attack Britain has experienced in three months, after the Westminster and the Manchester Arena attacks, May praised the efforts with which police responded to these terror attacks.
Britain's official terror threat had recently been lowered from "critical" after a bombing killed 22 people at an Ariana Grande concert in Manchester. "My thoughts go out to the victims and their loved ones".
"We cannot and must not pretend that things can continue as they are", she said, adding that "difficult" and potentially "embarrassing" conversations were needed within the United Kingdom about dealing with the spread of extremism.
"Donald Trump and those around him think that western liberal values are incompatible with mainstream Islam - London has proved him wrong".More news: Former Penn State Administrators Sentenced in Sandusky Scandal
"After the events last night in London, and those in Manchester just two weeks ago, we feel a sense of responsibility to honor those lost, injured, and affected", Braun said.
Asserting that the country is experiencing a new trend of brutal terror, May proposed to review counter-terrorism laws, and suggested longer sentences for some of the offences.
Labour leader Jeremy Corbyn said he was "absolutely shocked and horrified" at the attack, but added: "If we allow these attacks to disrupt our democratic process, then we all lose".
May called on worldwide communications companies to do more to block cyberspace to extremist groups who use it for recruitment and for encrypted information about plots.
Resuming the election campaign Sunday evening, Corbyn said, "You can not protect the public on the cheap".
Ms. May and her Conservative Party are facing an election on Thursday; she held a lead of just one percentage point in a recent poll. It is unclear how the unprecedented violence in the run-up to the election will impact voter sentiment.
Seven people died and almost 50 were injured when a van barreled into pedestrians on London Bridge, and then three attackers embarked on a stabbing spree at nearby Borough Market.More news: Donald Trump criticises Sadiq Khan's response to London attack
Khan said some of the injured were in critical condition.
Four French citizens were among the wounded.
Ms O'Neill said: "The attacks at London Bridge and Borough Market were horrific and I condemn them".
"We believe three people were involved, but we still have got some more inquiries to do to be 100% confident in that", he said.
A large police cordon remained in place in the area, south of the Thames River.
A Reuters reporter said some time after the attack began that he had heard loud bangs near the Borough Market area.More news: Afghanistan: At least 90 people lost their lives in Kabul attack
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