Donald Trump. Win McNamee/Getty Images President Donald Trump took to Twitter early Sunday morning to respond to the terror attacks that killed seven people and wounded dozens more in the heart of London late Saturday night.

"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 wrote.

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

London's mayor, Sadiq Khan, urged Londonders not to be alarmed by the increased police presence across the city following the attack. He released a video statement on Sunday morning asking that the city "remain calm and vigilant in the days ahead."

"We will never be cowed by terrorism," he said, calling the attackers "barbaric cowards."

Trump tweeted a third time on Sunday morning: "Do you notice we are not having a gun debate right now?" He wrote. "That's because they used knives and a truck!"

London police said the three attackers, who were shot dead by authorities just eight minutes after they arrived at the scene, used a vehicle to mow down pedestrians on London Bridge and then stabbed passersby at the nearby Borough Market.

At least 48 people were taken to five hospitals across London, according to the London Ambulance Service.

Trump drew criticism on Saturday night for failing to immediately reaffirm his support for the UK and express sympathy for victims, instead retweeting an unconfirmed Drudge Report story as London police were still responding to the incident.

The Drudge tweet said there were "fears of new terror attack after van 'mows down 20 people' on London Bridge," but the perpetrators, motive, and number of casualties involved in the incident were still unknown.

Trump then tweeted that "we need to be smart, vigilant and tough," and used the opportunity to push for his controversial immigration order that has been struck down by several federal courts.

"We need the courts to give us back our rights," he wrote. "We need the Travel Ban as an extra level of safety!"

His final tweet on Saturday night was one of condolence: "Whatever the United States can do to help out in London and the U. K., we will be there," Trump wrote. "WE ARE WITH YOU. GOD BLESS!"

US Secretary of Defense James Mattis declined to comment on the attacks on Sunday morning, telling reporters that he didn't "know enough about it yet."

"I like learning about something before I talk," Mattis said. "So let me look into it."

Prime Minister Theresa May made a strong — and possibly controversial — statement this morning, condemning "Islamic extremism" and the internet services companies who give it "the safe space it needs to breed."

"It is time to say 'Enough is enough,'" May said. "When it comes to taking on extremism and terrorism, things need to change."