Trauma surgeons in London said U.S. President Donald Trump had missed the point after he linked a wave of knife crime in the British capital to a ban on handguns.
Anger also flared in France after Trump, in a speech to the National Rifle Association (NRA), used his hands in a gesture to mimic the shooting of victims in Paris in 2015.
Trump, who is due to visit Britain on July 13, told members of the NRA in Dallas, Texas, on Friday that a "once very prestigious" London hospital, which he did not name, had become overwhelmed with victims of knife attacks.
"They don't have guns. They have knives and instead there's blood all over the floors of this hospital," he said. "They say it's as bad as a military war zone hospital. Knives, knives, knives, knives," he added, making stabbing gestures.
London suffered a spike in knife crime in the early part of this year, and the total number of murders during February and March exceeded that in New York.
Last month, trauma surgeon Martin Griffiths told the BBC that some of his colleagues had likened the Royal London Hospital in east London where he works to the former British military base Camp Bastion in Afghanistan.
"Some of my military colleagues have described their practice here as being similar to being at Bastion," he said. "About a quarter of what we see in our practice is knife and gun injury. And it's now we're doing major lifesaving cases on a daily basis."
But on Saturday he implied Trump had drawn the wrong conclusion from his remarks, saying on Twitter that he would be happy to invite Trump to his "prestigious" hospital to discuss London's efforts to reduce violence.
Griffiths posted his comment next to an animation of a stick figure with the phrase "The Point" flying over its head, and also linked to a statement on the hospital's website by a fellow trauma surgeon, Karim Brohi.
"There is more we can all do to combat this violence, but to suggest guns are part of the solution is ridiculous. Gunshot wounds are at least twice as lethal as knife injuries and more difficult to repair," Brohi said in the statement on Saturday.
Britain's government effectively banned handgun ownership in England, Scotland and Wales after a school shooting in 1996.
Diane Abbott, the opposition Labor Party's spokeswoman for home affairs, said she could "hardly see how violent crime in London justifies the licensing of guns in the U.S."
Trump's comments have caused upset before in Britain, which views itself as the United States' closest ally. Relations with Prime Minister Theresa May cooled last year after she criticized him for retweeting anti-Islam videos by a British far-right group.
Trump's NRA speech also drew anger in France on Saturday, after the U.S. president, using his hand in a gun gesture, acted out how a gunman had killed hostages one by one during an attack in Paris in November 2015.
Trump said a civilian could have stopped the massacre at the Bataclan concert hall, where 90 of the 130 victims of the attack died, had they had a gun.
Former French President Francois Hollande, who was head of state at the time, said on Twitter that Trump's comments and antics were "shameful" and "obscene."
Paris Mayor Anne Hidalgo said Trump's portrayal of the 2015 attacks was "contemptuous and unworthy."
