Three attackers drove a van into pedestrians on London Bridge before stabbing revelers nearby on Saturday night, killing seven people in what Britain called the work of Islamist militants engaged in a new trend of terrorism.
London Metropolitan Police said on Sunday 12 people had been arrested in the Barking district of east London in connection with the attack, which also injured at least 48 people, and raids were continuing there.
The attack occurred five days ahead of a parliamentary election and was the third to hit Britain in less than three months. Prime Minister Theresa May said the election would go ahead as planned on Thursday.