President Donald Trump has called the mass shooting at a music festival in Las Vegas an “act of pure evil”.

“My fellow Americans, we are joined together today in sadness, shock, and grief," the President said in an address to the nation. “Last night, a gunman opened fire on a large crowd at a country music concert in Las Vegas, Nevada. He brutally murdered more than 50 people, and wounded hundreds more. It was an act of pure evil.”

Mr Trump said we will visit the city on Wednesday.

As a mark of respect for the victims, the US flag will be flown at half-staff at the White House, military posts and naval stations, and upon all public buildings and grounds for the next week.

The FBI and Department of Homeland Security are working closely with local authorities in Las Vegas, Mr Trump said, to assist the investigation into the deadliest mass shooting in modern US history, with the death toll surpassing the 49 killed at a nightclub in Orlando in June 2016.

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

The alleged gunman, named as 64-year-old Stephen Paddock, opened fire from the 32nd floor of the Mandalay Bay Hotel and Casino, which is next to the concert site. Mr Paddock was found dead in a hotel room, police said.

Mr Trump praised first responders to the scene, saying “the speed in which they acted is miraculous and prevented further loss of life.”

“I want to thank the Las Vegas Metropolitan Police Department (LVMPD) and all of the first responders for their courageous efforts, and for helping to save the lives of so many,” Mr Trump said.

The President has spoken to Nevada Governor Brian Sandoval, Las Vegas Mayor Carolyn Goodman and LVMPD Sheriff Joseph Lombardo.