The shooter who killed at least 50 people in a LGBT nightclub in Florida called emergency services and swore allegiance to the head of ISIS, according to police.

Omar Mateen, who reportedly called 911 before the attack, shot down at least 50 people at the Pulse nightclub.

Islamic State, which is strongly anti-LGBT, has allegedly claimed responsibility for the shooting, according to ISIS-affiliated news agency Amaq, although an official claim from ISIS has been disputed.

Snapchat captures Orlando gunman firing 24 shots in 9 seconds

President Barack Obama said the shooter was a man “filled with hate” and called the incident the worst shooting in US history.

The 29-year-old, who was born in New York, was equipped with a handgun and an assault rifle.

The Council on American-Islamic Relations, the largest advocacy group for Muslims in the US, has asked the Muslim community to donate blood to those injured in the attack.

Rasha Mubarak, the Florida chapter’s Orlando regional co-ordinator, said: “We condemn this monstrous attack and offer our heartfelt condolences to the families and loved ones of all those killed or injured. The Muslim community joins our fellow Americans in repudiating anyone or any group that would claim to justify or excuse such an appalling act of violence.”

In pictures: Orlando nightclub shooting Show all 30 1 /30 In pictures: Orlando nightclub shooting In pictures: Orlando nightclub shooting Friends and family grieve after a list of hospitalised victims was released, implying the death of those who weren't on the list and hadn't been heard from, outside a Hampton Inn & Suites hotel near the Orlando Regional Medical Center AP In pictures: Orlando nightclub shooting People mourning for victims of the mass shooting near the Pulse gay nightclub in Orlando AFP/Getty Images In pictures: Orlando nightclub shooting Mina Justice speaks to a reporter discussing texting with her son Eddie who was in a bathroom at Club Pulse in Orlando. It has now been confirmed that Eddie Justice was among the 50 people killed in the massacre AP In pictures: Orlando nightclub shooting FBI agents investigate near the damaged rear wall of the Pulse Nightclub Getty Images In pictures: Orlando nightclub shooting Terry DeCarlo, executive director of the LGBT Center of Central Florida (C) is comforted by Orlando City Commissioner Patty Sheehan (R) after a shooting involving multiple fatalities at a nightclub in Orlando AP In pictures: Orlando nightclub shooting FBI agents investigate the damaged rear wall of the Pulse Nightclub Getty Images In pictures: Orlando nightclub shooting Police officials investigate the back of the Pulse nightclub after a shooting involving multiple fatalities at the nightclub in Orlando AP In pictures: Orlando nightclub shooting A member of the Medical Examiners office wheels a body to a vehicle from the mass shooting at Pulse Nightclub Getty Images In pictures: Orlando nightclub shooting A photograph posted by the Orlando Police Department on Twitter with the words, "Pulse shooting: In hail of gunfire in which suspect was killed, OPD officer was hit. Kevlar helmet saved his life", in reference to the operation against a gun man inside Pulse night club in Orlando REUTERS In pictures: Orlando nightclub shooting FBI, Orlando Police Department and the Orange County Sheriff's Office personnel investigate the attack at the Pulse nightclub in Orlando AP In pictures: Orlando nightclub shooting Annette Stubbs, a pastor at a local church, prays for victims a few blocks from a crime scene at the nightclub where a mass shooting took place AP In pictures: Orlando nightclub shooting Aimee McCarthy from Jacksonville, gives blood at the oneblood facility, to help the victims from a mass shooting at a nightclub in Orlando AP In pictures: Orlando nightclub shooting Police forensics investigators work at the crime scene of a mass shooting at the Pulse gay night club in Orlando REUTERS In pictures: Orlando nightclub shooting An injured person is escorted out of the Pulse nightclub after a shooting rampage AP In pictures: Orlando nightclub shooting An injured man is escorted out of the Pulse nightclub after a shooting rampage AP In pictures: Orlando nightclub shooting An injured man is escorted out of the Pulse nightclub after a shooting rampage AP In pictures: Orlando nightclub shooting Law enforcement officials work at the Pulse nightclub following a fatal shooting AP In pictures: Orlando nightclub shooting Orlando Police officers direct family members away from the nightclub AP In pictures: Orlando nightclub shooting The scene outside the Orlando gay club where multiple people have been shot AFP/Getty Images In pictures: Orlando nightclub shooting The injured are treated in the street outside Pulse in Orlando following the shooting EPA/Univision In pictures: Orlando nightclub shooting Two witnesses, Jermain Towns (left) and Brandon Shuford, wait down the street for news following shooting and hostage stand-off at the Pulse nightclub. Mr Towns said his brother was in the club at the time AP In pictures: Orlando nightclub shooting Emergency services at the scene. Ambulance crews and firefighters were outside the club alongside police. EPA In pictures: Orlando nightclub shooting People treating the wounded on the street EPA In pictures: Orlando nightclub shooting Friends and family members embrace outside the Orlando Police Headquarters during the investigation of a shooting at the Pulse night club Reuters In pictures: Orlando nightclub shooting Law enforcement agencies and local city representatives give a news conference in the wake of a mass-casualty shooting at the Pulse nightclub in Orlando Rex In pictures: Orlando nightclub shooting Orlando police officers seen outside of Pulse nightclub after a fatal shooting and hostage situation in Orlando, Florida Getty In pictures: Orlando nightclub shooting Friends and family console one another outside the Orlando Police Headquarters In pictures: Orlando nightclub shooting U.S. President Barack Obama speaks about the worst mass shooting in U.S. history that took place in Orlando REUTERS In pictures: Orlando nightclub shooting Imam Syed Shafeeq Rahman, the Imam of the mosqe that mass shooter Omar Mateen attended, speaks to the media in Fort Pierce. The imam said that the suspect never gave any indication he was capable of such violence.Omar Mateen attended evening prayers three or four times a week at the Islamic Center of Fort Pierce, bringing his son who is about four or five years old AFP/Getty Images In pictures: Orlando nightclub shooting Omar Mateen has killed 50 people at a gay nightclub after pledging allegiance to Isis in the deadliest mass shooting in US history Myspace