"Enough is enough," UK Prime Minister Theresa May has said, announcing a new push to deny extremists their "safe spaces" both online and in the real world.
There is "far too much tolerance of extremism in our country", the Prime Minister said, speaking outside 10 Downing Street after a meeting of the 'Cobra' emergency response committee in response to the London Bridge terror attack the night before.
Mrs May also proposed increasing jail sentences for terror offences and a review of counter-terror strategy.
Mrs May said it was the third terrorist attack on Britain in the last three months, and intelligence agencies and police had disrupted five credible plots since the Westminster attack in March.
The attacks in Westminster, Manchester and London Bridge were not connected in terms of planning and execution, Mrs May said.
"But we believe we are experiencing a new trend in the threat we face, as terrorism breeds terrorism."
Perpetrators were not only inspired by years of careful planning and training, but by "copying one another and often using the crudest of means of attack".
"We cannot and must not pretend that things can continue as they are," she said.
She said the attackers were bound by the "evil ideology of Islamist extremism" which was a perversion of Islam, and defeating this ideology was one of the greatest challenges of our time.
"It will only be defeated when we turn people's minds away from this violence and make them understand that our values, pluralistic British values, are superior to anything offered by the preachers and supporters of hate."
Mrs May said the terrorists' ideology must be denied the "safe space it needs to breed".
She said the internet and "the big companies that provide internet-based services" provided such spaces, and there should be new international rules regulating cyberspace to stop the spread of extremism.
She also said there were "safe spaces that continue to exist in the real world", in Britain.
"There is, to be frank, far too much tolerance of extremism in our country," Mrs May said.
"We need to become far more robust in identifying it and stamping it out across the public sector and across the society. That will require some difficult and often embarrassing conversations.
"We need to live our lives not in a series of separated segregated communities but as one truly united kingdom."
She also said there was a need to review Britain's counter-terrorism strategy to make sure police and security services had all the powers they needed, and to look at increasing jail terms for terror offences.
"It is time to say enough is enough. Everybody needs to go about their lives as they normally would??? but when it comes to taking on extremism and terrorism, things need to change."
Mrs May also confirmed that election campaigning would resume on Monday and the general election would go ahead as planned on Thursday.