After Khan told citizens of the city that they should not be alarmed by increased law enforcement presence, Trump tweeted, "At least 7 dead and 48 wounded in terror attack and Mayor of London says there is 'no reason to be alarmed!'"
Once representatives from Khan clarified he meant increased police presence was no cause for alarm, Trump tweeted more of his opinions about the London mayor.
This appeared to have rankled the notoriously thin skinned President, who added to his criticism this afternoon.
"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". MSM is working hard to sell it!'
British Prime Minister Theresa May was among those who came to Khan's defense.
After his election past year, Khan tweeted criticism of then-candidate Trump's rhetoric, saying his "ignorant view of Islam could make both our countries less safe".
Trump and Khan have spent the a year ago sniping at one another, largely over Trump's proposed travel ban that would temporarily bar some Muslims from entering the United States. "We are not going to let Donald Trump divide our communities", The Independent quoted Khan, as saying, while he addressed the media at the Tower Bridge last night.
"We must stop being politically correct and get down to the business of security for our people".
Trump's tweet drew controversy in the United Kingdom, where lawmakers accused the US president of smearing Khan's stance on terrorism.
President Donald Trump lashed out at his own Justice Department Monday for seeking the Supreme Court's backing for a "watered down, politically correct version" of the travel ban he signed in March.
"I think Sadiq Khan is doing a good job and it is wrong to say anything else", she said.
Asked what it would take for her to publicly criticize the US President, May suggested that she "was not afraid" to speak out when Trump "gets things wrong".
Khan, who belongs to the opposition Labour Party and is the first Muslim to be elected mayor of a major Western European city, is popular in London and his response to Saturday's killings has been widely praised as dignified.