As many as 49 people have been killed and dozens more injured in a mass shooting at the Pulse nightclub in Orlando, Florida.

Orlando Police Chief John Mina said the gunman entered opened fire at the Pulse nightclub at 02:00 (06:00 GMT) during a Latin themed night at the gay club.

The gunman, named by officials as 29-year-old US citizen Omar Mateen, exchanged fire with a police officer working at the club and a “hostage situation” unfolded.

Shortly after the situation began, the nightclub posted to its Facebook page:

“Everyone get out of pulse and keep running”

A number of the hostages trapped in the club managed to get messages to friends, family, and the police as the situation continued into the early hours of the morning.

They reported hearing “20, 40, 50 shots” and scenes “from a horror movie”.

At 05:00, Orlando Police made the decision to send a police assault team into the club.

Chief Mina said:

“Our Swat officers exchanged gunfire with the suspect, the suspect is dead.

“He appeared to be carrying an assault-type rifle and a handgun, and had some type of device on him.”

Orlando mayor Buddy Dyer has declared a “state of emergency” in the wake of the mass shooting, the worst in recent US history.