Islamic State (IS) has claimed responsibility for the shooting that killed over 50 people and wounded more than 400 in Las Vegas on Monday night (local time) - but FBI has doubts of the group's involvement.
The jihadist group says the gunman, Stephen Paddock, 64, converted to Islam a few months ago.
"The Las Vegas attack was carried out by a soldier of the Islamic State and he carried it out in response to calls to target states of the coalition," the group's news agency Amaq said in reference to the US-led coalition fighting the group in the Middle East.
"The Las Vegas attacker converted to Islam a few months ago," Amaq added.
There is however little evidence supporting claims of Isis involvement in the attack.
Mr Paddock turned the gun on himself at the end of the shooting, contravening typical IS conduct, where attackers aim to be martyred and die in suicide bombs or being shot by authorities.
A spokesperson for the FBI has also said there was currently no evidence Mr Paddock was involved with the terrorist group.
Aaron Rouse, special agent in charge of the FBI's field office in Las Vegas, told reporters: "We have determined to this point no connection with any international terror group."
Speaking to The Independent, Shiraz Maher, deputy director of the International Centre for the Study of Radicalisation and Political Violence, said that while the statement from Isis may be genuine actual involvement cannot be confirmed.
"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 said.
Reuters / Newshub.