Shooting erupted early on Sunday at a gay nightclub in Orlando, Florida and "multiple" people have been injured, police said.

The violence broke out at the Pulse nightclub, Orlando police said on Twitter, advising people to "stay away from area."

Local media reported that from seven to as many as 20 people had been shot in the incident, but had no further detail. The nightclub urged patrons in a post on its Facebook page to "get out" and "keep running."

Several patrons posted on social media that a gunman was holed up inside and holding hostages.

Video posted online showed a large response by police and emergency vehicles outside the nightclub.