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Orlando is now in a state of emergency after the gunman, identified as 29-year-old Omar Mateen, opened fire in the club before exchanging fire with the first responding police officer on the street. He then returned to the venue and took hostages, before finally being killed when a SWAT team burst into the club and rescued 30 people. In total, 50 people have died and another 53 have been rushed to hospital - several of whom are critically ill. The FBI spokesperson said: "Do we consider this an act of terrorism? Absolutely, we are investigating this from all parties' perspective as an act of terrorism. "Whether that is domestic terrorist activity or an international one, that is something we will certainly get to the bottom of. "We do have suggestions that the individual may have leanings toward that particular ideology. But right now we can't say definitively." A senior FBI official added the gunman had "leanings towards Islamic extremism." A photo from an Islamic State (ISIS)-affiliated Twitter account posted a photo of a man they identified as Mateen, further linking the attack with Islamic extremism.

Police said Mateen came from Port Saint Lucie in Florida. He had Afghan parents and had undergone weapons training. He was not on the US terrorism list but was being investigated for another unrelated crime. The Orlando sheriff also said his team are treating the incident as a "domestic terrorism incident." House homeland security chairman Michael McCaul added: “Our thoughts and prayers are with the victims of this senseless tragedy, their families and the people of Orlando. “This appears to be the worst terrorist attack on US soil since 9/11 and it is a sobering reminder that radical Islamists are targeting our country and our way of life. Americans will not be intimidated.”

REUTERS / ORLANDO POLICE At least 50 people have been killed in the biggest mass shooting in US history

US Senator for Florida Marco Rubio said the attack was indicative of the way Muslims treated gays and lesbians. He said: "If you look at the nature of the attack, it doesn't take an enormous amount of coordination to do this. "We have seen the way gays and lesbians are treated by radical Islam. So in some ways its not surprising. "If this is something inspired by radical ideology, common sense tells you he specifically targeted this community. "Unfortunately we've had a lot of practice at explaining this to our children. You have to explain that people are doing bad things. "I think we are learning that this is an individual who worked for a security company, so we will have to see what kind of background checks were done. "It is a reminder that the war on terror has evolved into something we never had to confront before."

REUTERS Shocked people gather outside Orlando Police headquarters

John Mina, Orlando police chief, said: "Multiple people are dead inside Pulse nightclub. At least 42 people have been transported to various hosptitals. "At 0500 hours this morning, the decision was made to rescue hostages that were in there. Our officers exchanged gunfire with the suspect. The suspect is dead." The gunman was wearing a suicide vest during his deadly spree, which began at around 2am local time (6am GMT). The shooting took place at Pulse, a gay nightclub in Orlando, where revellers were enjoying a night of music and dancing. The Orlando Fire Department called it's bomb and hazardous materials squad to the scene and carried out a controlled explosiona at 10am GMT. A handgun and an "AR-15" gun was found at the scene, along with a number of rounds.

REUTERS Distraught friends and family members gather after the worst mass shooting in US history

Orlando Mayor Buddy Dyer said: “Today we're dealing with something that we never imagined and is unimaginable.” President Barack Obama ordered the federal government to provide any assistance needed to Florida police while vice president Joe Biden “offered his prayers for all those killed and injured.” Orlando Regional Medical Centre was temporarily placed on lockdown but is now treating victims. The gunman is believed to have taken hostages in the club, with one reveller texting his mother: "He has us, he's in here with us." She has not had any contact with him since. The club's management posted on Twitter: "Everyone get out of Pulse and keep running."

WESH2 A victim being carried to safety following the nightclub shooting

REUTERS The FBI are treating the shooting as "an act of terrorism."

Ricardo Negron Almodovar said: “We heard rapid fire go off. In the room I was in, people went down to the floor. I wasn't able to see the shooter or people get hurt. "At some point, there was a brief pause, and a group of us got up and went to the exit that leads to the patio area outside. We found an exit and after that I just ran.” A witness said: "I was inside at 2am and someone started shooting. We just dove on the floor. Some of us just got up and ran out the back. After that we didn’t see any more of what happened."

ORLANDO POLICE Emergency services have rushed to the scene

Orlando Shooting: The world lights up to remember the 49 victims Tue, June 14, 2016 Orlando is now in a state of mourning as tributes pour in from all over the world. Play slideshow Getty 1 of 42 The world lights up to remember the victims of the Orlando Shooting

EPA Paramedics at the scene of this morning's "mass casualty situation"

One witness claimed he saw another gunman outside Pulse. He said: "We started hearing the shots and we were able to make it to a convenience store down the road, a 7/11. That’s when we saw another car shooting at the club. I would say [it went on for] 15 or 20 minutes, with the shooting back and forth. It was more than one person, from what we could make out."

SKY NEWS Emergency services at the scene in Florida this morning

FACEBOOK The warning Facebook post by Pulse nightclub this morning