The Islamic State group on Monday claimed responsibility for the Orlando shooting that killed 50 people, saying in a radio bulletin that it was carried out by "one of the soldiers of the caliphate".

"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," a bulletin from Al-Bayan radio said.

The jihadist group declared its "caliphate" in Syria and Iraq in 2014.