LONDON - London mayor Sadiq Khan has urged the police and security services to respond to questions about why they knew about Khuram Butt but did not act on warnings about his behaviour, reported Guardian newspaper.

Speaking on BBC Breakfast, Khan said: "Not unreasonably, these questions are being asked. I'm sure the police will look into what they knew, what they could have done, what they did do and if anything could have been done differently."

He acknowledged that there were thousands of potential suspects under consideration by the police.

But he added: "What we need to do is make sure that we ask these questions and the police and the security services respond and answer the legitimate questions we all have."

Khan said it will be harder to stop future terrorist attacks if Prime Minister Theresa May wins Thursday's general election and carries out planned changes to the Metropolitan Police's funding, reported Bloomberg.

In a statement that praised the "tremendous bravery" of police during the attack on Saturday night that left seven dead, Khan warned the British capital would lose between 3,400 and 12,800 officers if the premier pushes through budget cuts proposed by her Conservative Party.

"The Conservative plans mean another 400 million pounds (S$714 million) of cuts to the Met, as well as between 184 million pounds and 700 million pounds a year because of their changes to the police funding formula," Khan, a member of the opposition Labour Party, said in an e-mail.

"Cuts on this scale would make it harder to foil future terrorist attacks on our city and as Mayor of London I'm simply not willing to stand by and let that happen." Khan also criticised Theresa May's decision to invite Donald Trump on a state visit, amid his continuing spat with the president.