Islamic State's Amaq news agency has said that the Islamist militant group was responsible for the shooting that killed at least 50 people in a massacre at a gay nightclub in Orlando, Florida.
"The armed attack that targeted a gay night club in the city of Orlando in the American state of Florida which left over 100 people dead or injured was carried out by an Islamic State fighter," Amaq said on Sunday.
The gunman who conducted the worst mass shooting in US history at the club has been identified as Omar S Mateen, the US-born son of Afghan immigrants.
Police said he pledged allegiance to Islamic State during a conference call with federal law enforcement officials when his rampage was under way.
He also referenced the Tsarnaev brothers who carried out the 2013 Boston Marathon bombing, state police spokesman David Procopio said in an e-mail.
The Tsarnaev brothers killed three people and injured more than 260 in the April 15, 2013, attack.
Tamerlan Tsarnaev, 26, died four days later during a gunbattle with police while Dzhokhar Tsaranev, now 22, has been sentenced to death for his role in the attack.
Florida Senator Bill Nelson said the claim made by Amaq was not yet confirmed.
"The Islamic State's news agency has just issued a statement that says that they are responsible. That has not been confirmed," Nelson told reporters in Orlando.
"We'll have to see what those connections are once we get the details."