"Enough is enough" Theresa May says
Three attackers drove a van through a group of pedestrians on London Bridge Saturday night and then stabbing others nearby.
London police arrested 12 people and raids were continuing.
"It is time to say enough is enough," said Prime Minister Theresa May, just four days ahead of Thursday's election.
"We cannot and must not pretend that things can continue as they are," May said. She called for a tougher counter-terrorism strategy and new internet regulations.
The three assailants in Saturday's attack were shot dead by police.
May said this attack was not tied to the suicide bombing less that two weeks ago but was inspired a "single, evil ideology of Islamist extremism."
"While we have made significant progress in recent years, there is - to be frank - far too much tolerance of extremism in our country," she said.
Political campaigning will resume on Monday.
Update: A report says 21 of the injured people are in critical condition.
