In a tweet, Trump seized on comments by London Mayor Sadiq Khan, who said Britons should not be alarmed to see more police in the streets after three men drove a van into pedestrians on London Bridge before stabbing others nearby.

“At least 7 dead and 48 wounded in terror attack and Mayor of London says there is ‘no reason to be alarmed!’” Trump tweeted.

“We must stop being politically correct and get down to the business of security for our people. If we don’t get smart it will only get worse.”

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

In response, a spokesperson for the London mayor said Khan “is busy working with the police, emergency services and the government to coordinate the response to this horrific and cowardly terrorist attack”.

“He has more important things to do than respond to Donald Trump’s ill-informed tweet that deliberately takes out of context his remarks urging Londoners not to be alarmed when they saw more police – including armed officers – on the streets,” the spokesperson said.

Former US vice-president Al Gore told CNN he thought Trump’s tweet misrepresented what the mayor had said.

“I don’t think that a major terrorist attack like this is the time to be divisive and to criticise a mayor who’s trying to organise his city’s response to this attack,” said Gore.

Trump did not mention the mayor when speaking after a gala event at Washington’s Ford’s Theatre later on Sunday, where he condemned the attacks as an “evil slaughter” and said the United States would do everything in its power to assist the UK in bringing those responsible to justice.

“This bloodshed must end. This bloodshed will end,” Trump said.

Islamic State on Sunday night claimed responsibility for the attack via the militant group’s agency Amaq.

Four Australians were caught up in the incident, including Brisbane woman Candice Hedge, 34, who is recovering in hospital after her throat was slashed, and Darwin electrician Andrew Morrison, who is now flying home.

“There are two other Australians, so that brings it to a total of four, about whom we have very real concerns, but at this stage we’re not able to say anything more,” Prime Minister Malcolm Turnbull said this morning.

Turnbull said Australia wouldn’t be intimidated by terrorism and the “crazed criminals” peddling a corrupted interpretation of Islam.

“This is the work of cowardly, crazed criminals,” he told reporters in Sydney, adding that their evil message was a “blasphemous corruption” of Islam and millions of Muslims around the world.

“(They’re) trying to poison the religion from the inside and threaten all of our way of life.

“We defy them and we reject the poisonous ideology that they peddle. We will never give in to terrorism. We will never change the way we live.”

Earlier, Prime Minister Theresa May said Britain must be tougher in stamping out Islamist extremism.

It is time to say enough is enough

After the third militant attack in Britain in less than three months, May said Thursday’s national election would go ahead. But she proposed regulating cyberspace and said Britain had been far too tolerant of extremism.

“It is time to say enough is enough,” the Conservative leader said outside her Downing Street office, where British flags flew at half-mast.

“We cannot and must not pretend that things can continue as they are,” May said, adding that Britain was under attack from a new breed of crude copycat militants.

London police arrested 12 people in the Barking district of east London in connection with the attack and raids are continuing there.

Officers also shot dead the three male assailants in the Borough Market area near London Bridge within eight minutes of receiving the first emergency call shortly after 10pm.

Mark Rowley, head of counter-terrorism police, said eight officers had fired about 50 bullets to stop the attackers, who appeared to be suicide bombers because they were wearing what turned out to be fake suicide vests.

“The situation these officers were confronted with was critical: a matter of life and death,” Rowley said. “I am humbled by the bravery of an officer who will rush towards a potential suicide bomber thinking only of protecting others.”

A member of the public received non-critical gunshot wounds during the incident, he said.

Less than two weeks ago, a suicide bomber killed 22 children and adults at a concert by US singer Ariana Grande in Manchester in northern England. In March, in an attack similar to Saturday’s, five people died after a man drove into pedestrians on Westminster Bridge in central London and stabbed a policeman.

May said the series of attacks were not connected in terms of planning and execution, but were inspired by what she called a “single, evil ideology of Islamist extremism” that represented a perversion of Islam and of the truth.

She said this ideology had to be confronted both abroad and at home, adding that the internet and big internet companies provided the space for such extremism to breed.

Facebook said it wanted to make its social media platform a “hostile environment” for terrorists. Twitter also said it was working to tackle the spread of militant propaganda.

Witnesses described harrowing scenes as the attackers’ white van veered on and off the bridge sidewalk, hitting people along the way, and the three men then ran into an area packed with bars and restaurants, stabbing people indiscriminately.

One eyewitness said the attackers screamed “this is for Allah” as they stabbed people.

England’s health authority said on Sunday afternoon that 36 of those injured remained in hospital, of whom 21 were in a critical condition.

May made a private visit to staff and patients at King’s College Hospital, where some of the injured were being treated, a spokeswoman said.

The government announced that a nationwide minute of silence would be held at 11am on Tuesday to pay respect to the victims of the attack and flags would remain at half-mast on government buildings until Tuesday evening. A vigil will be held near London Bridge on Monday evening.

-Reuters/AAP