A gunman who police fear could have a bomb has reportedly taken several hostages after opening fire at a gay nightclub in Florida.

Local police said there were "multiple injuries" at Pulse in Orlando and warned people to stay away from the area.

A Facebook post by the club posted at 2am local time (7am UK time) said: "Everyone get out of Pulse and keep running".

Local TV reporter Stewart Moore said "more than 20 people have been shot" with an assault rifle and that the man remained barricaded inside the club with hostages.

He said there were fears the shooter may be wearing a bomb, and Orlando Fire Department's bomb squad and hazardous material team were at the scene.

Mr Moore said people were still trapped inside the club with gunshot wounds.

A police dispatcher told Agence France Presse: "There are injuries. I am not sure if there are any deceased at this time".

Witnesses reported seeing the shooter open fire around 2am.

Anthony Torres said on Facebook he "made it out just barely as we started to hear fire being shot" and "people are screaming that people are dead".

He said people were being "loaded up onto stretchers" outside the club.

One witness, Rosie Feba, told the Orlando Sentinel her girlfriend had said someone was shooting but she had assumed it was part of the music at first.

She said: "She told me someone was shooting. Everyone was getting on the floor.

"I told her I didn't think it was real, I thought it was just part of the music, until I saw fire coming out of his gun."

Ms Feba and her girlfriend ran out of the club, helping a man who had been shot on the way out.

The couple were shaken but unhurt.

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

Another witness, Ricardo J Negron Almodovar, said: "I was there. Shooter opened fire at around 2:00am.

"People on the dance floor and bar got down on the floor and some of us who were near the bar and back exit managed to go out through the outdoor area and just ran.

"I am safely home and hoping everyone gets home safely as well".

He said the gunman had begun shooting at the ceiling initially because the glass from the lights overhead was falling onto the dancefloor.

One Twitter user, Emilio, tweeted to say he and three others were hiding in a dressing room before later confirming he was "finally out, safe".

He said: "Please tell the cops we're at Pulse Orlando hiding in the dressing room there was a shooting.

"Four of us still hiding. Lights are off in club. Cops are here but haven't got us yet".

Amateur footage at the scene has recorded the sound of shots being fired outside the club.

Dozens of emergency vehicles are currently surrounding the club.

The motive for the attack is unknown.