President Donald Trump has called the London attacks an “evil slaughter” and says the United States will do everything it can in its power to assist the United Kingdom to bring those responsible to justice.

“This bloodshed must end. This bloodshed will end,” President Trump said in brief remarks after a gala event Sunday US time at Ford’s Theater in Washington.

On Saturday night, attackers killed at least seven people by ramming a van into pedestrians on London Bridge and stabbing revellers in nearby bars.

Police shot dead the three male assailants in the Borough Market area near London Bridge within eight minutes of receiving the first emergency call.

Whatever the United States can do to help out in London and the U. K., we will be there – WE ARE WITH YOU. GOD BLESS!

— Donald J. Trump (@realDonaldTrump) June 3, 2017

Earlier, London Mayor Sadiq Khan hit back at Mr Trump after the President accused him of suggesting that people should not be “alarmed” by terror attacks on the capital.

In a series of tweets the morning after the London Bridge atrocity, President Trump said it was time to “stop being politically correct”, adding: “At least seven dead and 48 wounded in terror attack and Mayor of London says there is ‘no reason to be alarmed!'”

A spokesman for Mr Khan said the comment was “ill-informed” and said the President had deliberately taken out of context remarks made by the mayor to reassure people about the increased police presence in the wake of the attack.

At least 7 dead and 48 wounded in terror attack and Mayor of London says there is "no reason to be alarmed!"

— Donald J. Trump (@realDonaldTrump) June 4, 2017

Speaking on the BBC, Mr Khan said he was advising Londoners and visitors not to be concerned by the presence of additional armed police officers on the streets of the capital in the days to come, and not playing down anxieties about the attack itself.

“My message to Londoners and visitors to our great city is to be calm and vigilant today,” he said.