Donald Trump has responded to an attack on festival-goers in Las Vegas in which at least 50 people have died, making it the deadliest mass shooting in US history.

"My warmest condolences and sympathies to the victims and families of the terrible Las Vegas shooting. God bless you!" he wrote.

The shooting, late on Sunday evening at a country music festival close to the city's casino strip, left more than 200 injured. The US President tweeted his condolences around five hours later, at just gone 7am, Washington DC time.

White House spokeswoman Sarah Huckabee Sanders said Mr Trump had been "briefed on the horrific tragedy in Las Vegas".

Ms Sanders said that "we are monitoring the situation closely and offer our full support to state and local officials. All of those affected are in our thoughts and prayers".

Las Vegas shooting – in pictures Show all 15 1 /15 Las Vegas shooting – in pictures Las Vegas shooting – in pictures People scramble for shelter at the Route 91 Harvest country music festival after gun fire was heard Getty Las Vegas shooting – in pictures People carry a person at the Route 91 Harvest country music festival after shots were fired David Becker/Getty Las Vegas shooting – in pictures People run from the Route 91 Harvest country music festival after gun fire was heard David Becker/Getty Las Vegas shooting – in pictures A handout photo released via Twitter by Eiki Hrafnsson (@EirikurH) showing concertgoers running away from the scene (C) after shots range out at the Route 91 Harvest festival on Las Vegas Boulevard EPA/Eiki Hrafnsson Las Vegas shooting – in pictures People lie on the ground at the Route 91 Harvest country music festival after hearing gun fire Getty Las Vegas shooting – in pictures A man in a wheelchair is taken away from the Route 91 Harvest country music festival after hearing gun fire David Becker/Getty Las Vegas shooting – in pictures People stand on the street outside the Mandalay Bay hotel near the scene of the Route 91 Harvest festival on Las Vegas Boulevard EPA/Paul Buck Las Vegas shooting – in pictures FBI agents confer in front of the Tropicana hotel-casino after a mass shooting during a music festival on the Las Vegas Strip Reuters/Las Vegas Sun/Steve Marcus Las Vegas shooting – in pictures Las Vegas police run by a banner on the fence at the Route 91 Harvest country music festival grounds after shots were fired David Becker/Getty Las Vegas shooting – in pictures An injured person is tended to in the intersection of Tropicana Ave. and Las Vegas Boulevard after a mass shooting at a country music festival Ethan Miller/Getty Las Vegas shooting – in pictures Metro Police officers pass by the front of the Tropicana hotel-casino after a mass shooting at a music festival on the Las Vegas Strip Reuters/Las Vegas Sun/Steve Marcus Las Vegas shooting – in pictures A woman sits on a curb at the scene of a shooting outside of a music festival along the Las Vegas Strip AP/John Locher Las Vegas shooting – in pictures A cowboy hat lays in the street after shots were fired near a country music festival in Las Vegas Getty Las Vegas shooting – in pictures Las Vegas Metro Police and medical workers stage in the intersection of Tropicana Avenue and Las Vegas Boulevard South after a mass shooting at a music festival on the Las Vegas Strip Reuters/Las Vegas Sun/Steve Marcus Las Vegas shooting – in pictures Sheriff Joe Lombardo (2-R) speaking during a press briefing in the aftermath of the active shooter incident on Las Vegas Boulevard EPA

Mr Trump is due to visit the storm-ravaged US territory of Puerto Rico on Tuesday, having engaged in a public spat with officials on the island after they accused him of inaction following devastation caused by Hurricane Maria.

There has been no comment from the White House on whether that trip will be rearranged in the wake of the Las Vegas massacre.

Following the attempted bombing of a Tube train at Parsons Green station in London last month, Mr Trump tweeted that it was an attack by a “loser terrorist” and called on authorities to be “proactive”.

Police in Las Vegas have said they are not treating the mass shooting as an act of terrorism, despite Nevada state law defining terror as “any act that involves the use or attempted use of sabotage, coercion or violence which is intended to cause great bodily harm or death to the general population”.

Theresa May and Boris Johnson were among the first world leaders to respond to the killing.

The Prime Minister said her thoughts were with the victims and emergency services following the "appalling attack".

The Foreign Secretary said he was "horrified" by the shooting, adding: "The United Kingdom stands with the American people against this indiscriminate violence. My thoughts are with all those caught up in it.