Florida: The gunman behind the attack on a gay nightclub in Florida that left 50 dead is a 'soldier of caliphate', said the Islamic State of Iraq and the Levant group on Monday in a radio bulletin.
The suspect, 29-year-old Omar Mateen, is a Muslim American of Afghan descent and law enforcement agencies were investigating whether he had ties to or was inspired by Islamist extremism after a source had linked to the Islamic State group claimed the attack.
The Islamic State group claimed responsibility for the Orlando shooting and in a bulletin from Al-Bayan radio, it said: "God allowed Omar Mateen, one of the soldiers of the caliphate in America, to carry out an attack entering a crusader gathering in a night club... in Orlando in Florida, killing and wounding more than 100 of them."
The jihadist group declared its "caliphate" in Syria and Iraq in 2014.
The IS-linked news agency Amaq said on Sunday that the attack had been "carried out by an Islamic State fighter".
The FBI said Mateen apparently made a 911 call just before the massacre to claim allegiance to the Islamic State group.
Sunday`s attack, the worst mass shooting in modern US history, was carried out at Orlando`s Pulse nightclub, a well-known gay hangout.
US President Barack Obama said the FBI was investigating the killings "as an act of terrorism".