An unknown number of people were injured in a shooting incident at a gay nightclub in Orlando in the state of Florida early Sunday, and the gunman was dead, the police said.

It was not immediately clear how many people were injured, but Orlando police said on Twitter that there were "multiple injuries" in the violence that broke out the Pulse nightclub.

"Shooting at Pulse Nightclub on S Orange. Multiple injuries. Stay away from area," it said.

"The shooter inside the club is dead," police also tweeted.

Media reports said the shooting incident broke out around 2 a.m., with witnesses saying they heard multiple gunshot and the shooter most probably used automatic weapons.

Images posted by social media users showed a huge response by local police, with emergency vehicles seen at the scene.

The shooting incident came just one day after Christina Grimmie, a singer who gained fame on YouTube and contesting the "The Voice," was shot dead while signing autographs after a concert in Orlando.