A gunman opened fire in a gay nightclub called Pulse in Orlando, Florida, killing 50 people late on Saturday night. At least 53 people were injured in the attack by a man identified as 29-year-old Omar Mateen, an American citizen living in Port St Lucie, Florida. The Islamic State has taken responsibility for the shooting in its news agency, Amaq. "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 was reported as saying by Reuters.

Mateen was killed by police in a gunbattle inside the club. He had reportedly taken hostages after he shot at people inside the club. The incident is being called an act of terror by investigative agencies.

As the attack began at 2 am (local time), the club urged patrons to flee. “Everyone get out of Pulse and keep running,” the Facebook page of Pulse Cub posted. Orlando Police Chief John Mina told reporters, "It appears he was organised and well-prepared," the chief said, adding that the shooter had an assault-type weapon, a handgun and "some type of (other) device on him." Orlando Mayor Buddy Dyer told the media said he had declared a state of emergency for Orlando, and that he also asked the governor to do the same for the state, CNN reported.

Social media has been flooded with videos showing injured people being treated outside the club in Orlando. The police said they are responding to the situation with several emergency vehicles already stationed at the spot, reported the Orlando Sentinel. A bomb squad and teams that deal with hazardous materials were also sent to the scene. Mina also said that the investigation is likely to be lengthy because of the number of victims.

Many victims remain unidentified, while families await news from officials about their relatives. Though the reason for the shooting remains unknown, Congressman Alan Grayson has said it was "no coincidence" the attack happened in a gay club.

The attack, which some agencies are calling "the deadliest mass shooting in US history", incidentally comes a day after The Voice singer Christina Grimmie was shot dead at a concert venue also in Orlando. However, the two shootings do not appear to be related.