The authorities in the US city of Orlando have been giving more details of the gun attack on a gay club in which 49 people were killed.

Gunman Omar Mateen opened fire in the early hours of Sunday morning in the deadliest mass shooting in recent US history, which left 53 people injured.

Police chief John Mina said an off-duty officer working at the club had engaged Mateen in a gun battle.

Shortly after, more police officers arrived while the suspect was shooting.

They engaged Mateen in a gun battle, forcing him to retreat to the bathroom, Mr Mina said, where he held hostages.

At that time, "dozens and dozens" of people were able to be rescued from the Pulse nightclub, the police chief said.

Mateen was on the phone with police from the bathroom, Mr Mina said, and made a pledge of allegiance to so-called Islamic State while speaking to them.

Orlando Mayor Buddy Dyer praised the "heroic acts" of the city's police department, law enforcement agencies and citizens.