The prime minister has said “it is time to say enough is enough” as she condemned a terror attack on “innocent and unarmed civilians” which left seven people dead and 48 injured in London.
A white van hit pedestrians on London Bridge at about 22:00 BST on Saturday, then three men got out and stabbed people in nearby Borough Market.
The three attackers, who wore fake bomb vests, were shot dead by police.
Mrs May said the UK’s counter-terrorism strategy would be reviewed.
It is the third terror attack in the UK in three months, following the car and knife attack in Westminster in March, which left five people dead, and the Manchester bombing less than two weeks ago, in which 22 people were killed.
Most political parties have suspended national general election campaigning, but Mrs May said full campaigning would resume on Monday and the general election would go ahead as planned on Thursday.
Eyewitnesses to the attack described seeing a white van travelling at high speed along London Bridge, hitting pedestrians, before crashing close to the Barrowboy and Banker pub.
BBC reporter Holly Jones, who was on the bridge, said it was “probably travelling at about 50 miles an hour” and hit “five or six people”.
Three men then got out and began attacking people in the nearby market – an area known for its bars and restaurants, which were busy on a warm summer evening.
Terrified drinkers rushed away from the scene, some taking shelter in London Bridge Underground station.
‘Rampage’
One witness, Gerard, told the BBC he saw a woman being stabbed “10 or 15 times” by men shouting “This is for Allah”.
Another, Eric, told the BBC the men “ran towards the people that they nearly ran over”.
“I thought, ‘Oh maybe they’re worried about them and trying to comfort them…’
“[Then] they literally just started kicking them, punching them, they took out knives… it was a rampage really.”
The three suspects were shot dead within eight minutes of the first 999 call being received.
Metropolitan Police Commissioner Cressida Dick praised the “extraordinary bravery” of her officers, on and off duty, who risked their lives by rushing to confront the attackers.
She said she understood there could be a certain amount of “fear” among Londoners, but added: “The last thing we need is people over-reacting or taking out their frustrations on people in other communities or in their own communities.”