US President Donald Trump honed in on knife crime in London in a speech justifying the right to own guns in the US.

"I recently read a story that in London, which has unbelievably tough gun laws, a once very prestigious hospital, right in the middle, is like a war zone for horrible stabbing wounds," he said on Friday.

He made the comments at a meeting of the National Rifle Association, which campaigns to protect the US Second Amendment giving Americans the right to bear arms.



The president appeared to refer to a Daily Mail article published last month in which Martin Griffiths, a trauma surgeon at Barts Health NHS Trust, said he was treating children as young as 13 for stab wounds, and compared scenes in the hospital to an "Afghan war zone".

"Yes, that's right, they don't have guns, they have knives, and instead there's blood all over the floors of this hospital," Trump said. "They say it's as bad as a military war zone hospital. Knives, knives, knives. London hasn't been used to that. They're getting used to it. It's pretty tough."