British police detained a number of people during early morning raids in east London on Monday as part of an investigation into an attack that killed seven people and injured around 50 on Saturday night.
In the third major militant assault to hit Britain in less than three months, attackers rammed a van into pedestrians on London Bridge before stabbing revellers in nearby bars.
Prime Minister Theresa May will chair a meeting of the government's emergency response committee on Monday to discuss the response to the attack which comes ahead of a national election on Thursday.
Police had already arrested 12 people in the Barking district of east London over the weekend and they said on Monday they had entered two premises in Newham and Barking at 0315 GMT and detained "a number of people". They said searches were ongoing at both addresses.