Isis has claimed responsibility for the deadliest mass shooting in modern American history as it continues to lose territory in its self-declared “caliphate”.

Police said at least 58 people were killed and 500 victims wounded when a gunman opened fire on dense crowds at a concert in Las Vegas.

Officials have identified the shooter as Stephen Paddock, a 64-year-old white American who had multiple weapons on the 32nd floor of a nearby hotel, where he is believed to have killed himself.

A statement published by the group's Amaq propaganda agency claimed the attacker was a “soldier of the Islamic State”.

“The Las Vegas attacker is a soldier of the Islamic State in response to calls to target coalition countries,” it said.

Isis also claimed the gunman “converted to Islam several months ago”, without providing more details. Paddock's religion and lifestyle have not yet emerged elsewhere.

The wording of the release is similar to other attacks that have been inspired, rather than directed, by Isis.

But Paddock's alleged suicide would differ from the actions of the vast majority of Isis attackers, who seek to be “martyred” in bombings or by security forces, suggesting he had little, if any, guidance from the group.

Shiraz Maher, deputy director of the International Centre for the Study of Radicalisation and Political Violence (ICSR), said the statement was authentic but it was too early to confirm Isis involvement.

“We can say the message is definitely coming from Isis, but whether Isis is just doing this as psychological warfare against the US remains to be seen,” he told The Independent.

“The more we learn about the history of the gunman, the more we will know.

“If he had converted, somebody somewhere would know. If it’s true he would have had to have some contact with Isis [and] it would strike me that this guy would have had some sort of contact, some sort of electronic signals that authorities will dig into over the coming days.”

A spokesperson for the FBI said no link to Isis had yet been found in the ongoing investigation, with analysis of Paddock’s phone and electronic devices incomplete.

“As this event unfolds we have determined to this point no connection with an international terrorist group,” he added.

“As this investigation continues we will continue to work with our partners.”

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

Isis’ claim, which cannot be independently verified, came days after it released a speech purporting to be from the group's leader.

A 46-minute audio recording appeared to show Abu Bakr al-Baghdadi praise the jihadis killed in the battle to retake Mosul and other former Isis territories.

He urged followers to “intensify one attack after another against the infidels”, following a spike in global terror attacks.

Isis has released several rounds of detailed guidance on how to carry out mass casualty terror attacks, including how to obtain guns and naming concerts as a prime target.

An issue of its English-language propaganda magazine released in May said it was “very simple” to obtain firearms in the US, directing followers to gun shows and online dealers.

The same issue named concert halls and entertainment venues among target locations because of the density of contained crowds, citing the “blessed” massacres at the Bataclan during the Paris attacks and Omar Mateen’s shooting at the Pulse nightclub in Orlando as “outstanding” examples.

Security officials and experts have long warned that Isis will seek to maintain momentum and legitimacy through terror as its so-called “caliphate” dwindles in Iraq and Syria.

The group's claims can be difficult to confirm or deny, with one alleging that explosives were planted at Charles de Gaulle airport recently disproved after being published in its al-Naba propaganda newspaper.

A Las Vegas Metropolitan Police officer stands near the scene of a mass shooting at a country music festival (Ethan Miller/Getty Images)

Conversely, Isis has also failed to claim responsibility for several attacks carried out by potential supporters, including a deadly knife rampage in Hamburg and terrorist stabbing in Finland.

Raffaello Pantucci, the director of international security studies at the Royal United Services Institute (Rusi) think-tank said “nothing could be discounted” in Las Vegas.

“There’s always that dilemma when you look at individuals who launch attacks,” he told The Independent.

“How do we know he’s not just excising his own personal demons and using this method of attack to attract attention? It may be impossible to ever know.”

Mr Pantucci said an unbalanced individual already attracted to committing a violent act may latch onto Islamist ideology for “meaning and resonance”, as well as the infamy that the association provides.

“And from the group’s perspective it’s a win for them,” he added. “The public conversation is about Isis and that’s what they want.”

There was initial scepticism over Paddock’s supposed affiliation following revelations that he had been a gambler and was not known for extremism by relatives.

His brother claimed he was “not an avid gun guy at all”, with “no religious affiliation, no political affiliation” or history of mental illness.

Eric Paddock told CBS his brother was a gambler, saying: “The fact that he had those kinds of weapons is just...where the hell did he get automatic weapons? He has no military background or anything like that.

"He's a guy who lived in a house in Mesquite and drove down and gambled in Las Vegas."

Paddock is believed to have killed himself before a police Swat team burst into his room at the Mandalay Bay Hotel and Casino, where at least 10 ”rifles“ were found, police said.

Las Vegas Metropolitan Police in front of a sign for the Route 91 Harvest festival (EPA)

"We have no investigative information or background associated with this individual that is derogatory,” Clark County sheriff Joseph Lombardo told reporters.

"The only thing we can tell is he received a citation several years ago, and that citation was handled as a matter of normal practice in the court system.”

Guns and ammunition were found in a search of Paddock's two-bedroom home, where he had lived with girlfriend Marilou Danley, 62.

Mr Paddock said the family was “shocked, dumbfounded” by what happened, adding: “He was just a guy. Something happened, he snapped or something.”

Dr Maher said there was “absolutely no profile” for an Isis terrorist, with the known examples in Britain alone coming from different background ranging from criminals to graduates, the unemployed and the affluent.

Mr Pantucci said too little was known about Paddock to speculate on his motivations, but that there was a possibility that he had viewed Isis propaganda and communication with the group could not be dismissed offhand.

He added that some Muslim converts are drawn in by radical individuals, with a growing body of research indicating that those with lower levels of religious knowledge are more easily convinced by Isis ideology.

The shooting at the Route 91 Harvest Festival started shortly after 10pm local time, with footage showing concert-goers throwing themselves to the ground and running as several extended rounds of automatic gunfire rang out.

It came after the group claimed responsibility for a stabbing attack that left two young women dead in the French city of Marseille earlier on Sunday.