Las Vegas, (IANS) At least 50 people were killed and more than 200 injured in a mass shooting at a country music concert here. The lone attacker was later killed by the police.

Las Vegas Metro Police Sheriff Joseph Lombardo confirmed the death toll in the attack at the city's Route 91 Harvest Festival, and called it the "deadliest mass shooting in US history".

The gunman opened fire into the outdoor country music festival from the 32nd floor of Las Vegas' Mandalay Bay Resort and Casino at 10.30 p.m. on Sunday while singer Jason Aldean was performing on stage. The attacker was shot dead by the police later, CNN reported.

The suspect acted alone and was identified as 64-year-old local resident Stephen Paddock. He was not found to be associated with any terrorist activity, said Lombardo.

The police were hunting for Paddock's female companion, Marilou Danley, who they said was travelling with him before the attack, CNN reported.

US President Donald Trump posted a tweet offering his sympathies to those caught in the Las Vegas attack.

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

Off-duty police officers were among the dead, said Lombardo. Two other police officers were also being treated for injuries.

Bursts of shots could be heard in videos shared on social media, which showed scenes of people running away and trying to protect themselves.

"We heard what sounded like firecrackers going off. Then all of a sudden we heard what sounded like a machine gun. People started screaming that they were hit ... when we started running out there were probably a couple hundred on the ground," said Meghan Kearney, who attended the music festival.

"People kept dropping and dropping ... People were getting shot one foot away from us," she said. "People were trying to save their friends. There were gunshots everywhere. Helping them would've meant that we got shot too."

Police tweeted that they were "searching for two vehicles associated with the shooter: Hyundai Tucson Nevada/114B40 and a Chrysler Pacifica Nevade/79D401".

Leaders from around the world reacted to the horrific shooting. UK Prime Minister Theresa May condemned the "appalling attack" in a tweet from the Prime Minister's official Twitter account.

"PM - The UK's thoughts are with the victims and the emergency services responding to the appalling attack in Las Vegas," the tweet said.

"A deeply sad day for the city of Las Vegas," wrote London Mayor Sadiq Khan on Twitter. "London sends our condolences to the victims and their families."

Australian Prime Minister Malcolm Turnbull tweeted: "Australia mourns with America tonight after shocking senseless attack in Las Vegas."

Swedish Prime Minister Stefan Löfven and his Danish counterpart Lars Løkke Rasmussen also tweeted in support of the victims.