US President Donald Trump on Sunday criticised London Mayor Sadiq Khan for asking the British public to remain calm after the weekend terrorist attack.

Trump once more resorted to Twitter early Sunday morning to send a message that "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."

Trump was referring to the Saturday night terrorist attack in London that left seven victims and three terrorists dead, along with dozens of civilians wounded, Efe reported.

The US president once again let diplomatic niceties fall by the wayside as he criticised Khan, a Muslim with whom he had already developed a tense relationship, for seeking to reassure Londoners, and other Britons, after the attack, although he took the mayor's remarks out of context.

"At least 7 dead and 48 wounded in terror attack and Mayor of London says there is 'no reason to be alarmed!'" Trump tweeted, apparently misunderstanding Khan's earlier statement.

"Londoners will see an increased police presence today and over the course of the next few days – no reason to be alarmed," Khan had said in a statement broadcast on the BBC.

"One of the things police and all of us need to do is make sure we're as safe as we possibly can be."

"Do you notice we are not having a gun debate right now? That's because they used knives and a truck!" Trump went on to say in yet another tweet.

Meanwhile, one of the mayor's spokesmen said on Sunday in response to Trump's tweets that Khan had "more important things to do" in terms of overseeing the city's response and recovery.

"The mayor is busy working with the police, emergency services and the government to coordinate the response to this horrific and cowardly terrorist attack and provide leadership and reassurance to Londoners and visitors to our city," the spokesman said.

"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 Saturday evening attack, in which three attackers in a van mowed down a number of pedestrians on London Bridge and then stabbed many more at nearby Borough Market before being gunned down by police, comes just four days before Britain's national election on Thursday.

Seven people lost their lives in the attack and 48 were wounded or injured, of which 36 remain hospitalized, 21 of them in critical condition.