Media playback is unsupported on your device Media caption Trump: Blood on London hospital floor

US President Donald Trump has criticised the level of knife crime in London, comparing one of the city's hospitals to a "war zone".

His comments came in a speech to the National Rifle Association (NRA), in which he defended US gun laws.

He also told the firearms lobby's conference in Dallas, Texas, that American gun rights were "under siege".

Mr Trump is due to visit the UK this summer, after previously cancelling a trip amid calls for mass protests.

"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.

"They don't have guns. They have knives and instead there's blood all over the floors of this hospital.

"They say it's as bad as a military war zone hospital. Knives, knives, knives, knives." He mimed a stabbing motion.

"London hasn't been used to that. They're getting used to it. It's pretty tough."

It is unclear where Mr Trump sourced his information. However, leading London trauma surgeon Dr Martin Griffiths told BBC Radio 4 a month ago that his hospital was likened to an Afghan war zone. The interview was the basis for a Daily Mail article.

The surgeon, who works at the Royal London Hospital, responded to Mr Trump on Twitter with an image suggesting the president had missed the point, adding that he was "happy to invite Mr Trump to my prestigious hospital".

Dr Griffiths had told the BBC last month about treating stabbing victims "on a daily basis".

He said: "Some of my military colleagues have described their practice here as being similar to being at [Helmand province's former Camp] Bastion."

He added: "We routinely have children under our care, 13, 14, 15 years old are daily occurrences, knife and gun wounds."

At least 38 people in London have lost their lives to knife crime so far this year, the Met Police has said.

It is not the first time Mr Trump, who will visit the UK on 13 July, has remarked on security in the UK capital.

Last year he criticised London Mayor Sadiq Khan for his handling of terrorist attacks in the city.

The Met Police and Mr Khan declined to comment on Mr Trump's latest remarks.

Marian Fitzgerald, a criminologist at the University of Kent, said although there had been a spike in knife-related deaths in London, it was a separate issue to gun control.

She told BBC Radio 4's Today programme: "It's just politically convenient, in a speech to the gun rights lobby, to try and make those comparisons and they are totally spurious.

She added: "If he needs reassurance, Donald Trump is going to be much safer in London than he would be at home."

Mr Trump also claimed that the terror attack in Paris in 2015 - in which 130 people were killed - could have been prevented if more people had been armed.

"The terrorists would have fled or been shot and it would have been a whole different story," he said.

It was Mr Trump's fourth address to the NRA and his second in office. The last president to do so was Ronald Reagan in 1983.

An estimated 80,000 people have attended this year's NRA convention in Dallas.

The lobby supported Mr Trump during his 2016 presidential election, spending more than $11m (£8m) in advertisements for him, according to the Center for Responsive Politics.

After a high school shooting in Parkland, Florida, left 17 dead in February, Mr Trump said he would "fight" the NRA on gun control.

At the time, the president appeared to support raising the age limit of purchasing rifles, closing background check loopholes and confiscating firearms from mentally ill individuals.

Media playback is unsupported on your device Media caption How young conservatives view #NeverAgain

The US president later said there was "not much political support".

Mr Trump instead pushed a proposal to provide firearms training to school employees.

His administration, however, has taken steps to ban bump stocks, which allow a rifle to shoot hundreds of rounds a minute.

More on guns in the US