Hours after the Islamic State appeared to claim responsibility for the mass shooting in an Orlando gay club on Saturday night, United States officials said there was no direct evidence linking them to the crime, Reuters reported. Three officials of the Federal Bureau of Investigation told the news agency that the information so far is that the shooter, Omar Mateen, had made a pledge of loyalty to the militant group for the first time during the massacre. Mateen had reportedly called emergency line 911 and said he was allied with the Islamic State.

Soon after, the terror group had purportedly made a statement on an online agency Amaq, which is associated with it. “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,” the message had said. However, officials said further investigations are required to confirm that the group had a hand in the attack, which killed 50 people and left more than 50 others injured.

US President Barack Obama said, “We know enough to say that this was an act of terror and an act of hate,” in an address to the nation. He added, "This is an especially heartbreaking day for our friends who are lesbian, gay, bisexual or transgender.”

Mateen’s former wife Sitora Yusufiy, who divorced him in 2011, told CNN that his actions were caused by a mental illness, not a link to the Islamic State or any religious fundamentalism. She claimed that during their marriage, it became evident that he was “bipolar, abusive and unstable”.

The attack took place around 2 am at Pulse, a large club that has room for nearly 300 patrons. The club was hosting a “Latin flavor” event, when Mateen arrived on the scene and started shooting. Authorities at the venue asked people to run as soon as they could. The Mayor of Orlando Buddy Dyer told the media he had declared a state of emergency in the city, and that he also asked the governor to do the same for the state. Mateen was eventually killed by police in a gunbattle inside the club. The incident is being described as the worst mass shooting in US history.