US President Donald Trump has denounced the Las Vegas massacre as "an act of pure evil" as the death toll from the deadliest mass shooting in US history climbed to 59.

A further 527 people are in hospitals after Stephen Craig Paddock, 64, opened fire on a country music festival before killing himself on Sunday night local time (Monday AEDT).

Stephen Paddock, 64, took his own life after he shot dead at least 50 people and injured more than 400 others.

In a sombre address from the White House several hours after the massacre, Mr Trump said Americans are joined together in “sadness, shock and grief”.

He also praised the "miraculous" response of authorities who he said prevented further loss of life by locating Paddock so swiftly.

The president added flags across the country will be lowered to half-mast as a mark of respect to the victims, and said he will visit Las Vegas on Wednesday.

“We pray for the day evil is banished…may God provide the grieving families with the strength to carry on,” Mr Trump said.

Read more: Australians caught up in Las Vegas shooting

Paddock had at least eight rifles in his hotel room on the 32nd floor of the Mandalay Bay Resort and Casino, where he opened fire on more than 22,000 people at the Route 91 Harvest country music festival below.

People are shown running from the concert. (Getty Images) (Getty Images)

Police crouch behind a patrol car with their weapons trained on the casino. (Getty) (Getty Images)

The FBI has refuted claims by the Islamic State group who took responsibility for the attack, saying it was carried out by a "soldier" who "converted to Islam several months ago".



"The executor of the Las Vegas attack is a soldier of the Islamic State and he carried out the operation as a response" to calls to target countries engaged in military action against the jihadists," ISIS's propaganda outlet Amaq said in online statements.

The FBI said there was “no connection” to the ISIS claims.

Police originally said Marilou Danley was a person of interest but she was later found to be 'out of the country' during the shooting. (AAP)

“We have determined at this point no connection with the international terrorist group,” a spokesman said.

“We will continue to work with our partners to make sure this is thoroughly investigated.”

Festivalgoers are seen running from the event at the Mandalay Bay Resort and Casino. (Getty Images) (Getty Images)

A body, which has been pixelated, lies on the ground amid rubbish at the concert. (Getty Images) (Getty Images)

Police said they have completed their search of Paddock’s property in Mesquite and are now searching another property in northern Nevada.

They added neighbours had to be evacuated as they search the property.

Police said Paddock acted alone, but earlier launched an appeal to find a "person of interest"- a woman who is believed to be an Australian who moved to the US 20 years ago.

She has since been ruled out as a suspect.



Las Vegas Metro Police Sheriff Joseph Lombardo said Marilou Danley, a "companion" of Paddock's, was found out of the country.



Mr Lombardo said police believed Ms Danley was not involved in the massacre, though Paddock "was utilising some of her identification" and the pair lived together in Mesquite.

Festivalgoers are seen running from the event at the Mandalay Bay Resort and Casino. (Getty Images) (Getty Images)

The Australian Department of Foreign Affairs and Trade (DFAT) told 9news.com.au it is "aware" of reports Ms Danley is Australian.

"Given the local authorities are still investigating the incident, we cannot comment further on these reports," a spokesperson said.

The identities of the dead and injured have not yet been released as police work to contact their families.

It was confirmed an unnamed off-duty Las Vegas officer was killed and two others injured.

DFAT said it is making "making urgent enquiries with local authorities to determine whether any Australians have been affected" by the shooting.

Las Vegas authorities are now calling for blood donations to assist the injured.

Mr Trump earlier tweeted his "condolences" to the victims of the shooting.

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