Orlando's mayor announced on Sunday that an attack on a gay club in the Florida city left at least 50 dead and 53 others injured.

US Representative Alan Grayso said the shooter was identified as Omar Mateen, a US citizen with Afghan roots. The man was in his late twenties, the lawmaker added.

"We have cleared the building, and it is with great sadness that I share we have not 20 but 50 casualties in addition to the shooter," Orland Mayor Buddy Dyer told a press conference.

"There are another 53 that are hospitalized," he added.

Saturday's attacks marks the one of the worst mass shooting in US history, according to AFP news agency.

'Suspect is dead'

A policeman first engaged a suspect at the entrance of the Pulse club after he started firing around 2 am local time. The shooter then entered the club, turning the firefight into a hostage situation, Orlando police chief John Mina said.

"At approximately 0500 the decision was made to rescue hostages that were in there," he said.

A SWAT team moved in and killed the attacker on the premises.

"The suspect is dead; he appeared to be carrying an assault type rife, a handgun, and some kind of device with him," Mina added.

The assailant appeared to have been prepared for the attack, according to the police. An FBI spokesman said that the shooting was being investigated as an act of terrorism.

Witnesses reported that the gunman used an automatic weapon.

Club visitor Jon Alamo said he was in the back of one of the club's rooms when an armed man came into the front.

"I heard 20, 40, 50 shots," Alamo said. "The music stopped."

'Last sip'

Another patron, Rob Rick, said the incident took place around closing time on Sunday morning, with around 100 people still inside.

"Everybody was drinking their last sip," he said.

When the shooting occurred, around 2 a.m. local time (0800 GMT), the club, on Facebook, warned people to "get out of pulse and keep running."

Multiple emergency vehicles were reported to have been dispatched to the scene, including the Fire Department's bomb squad and hazardous material team.

The police said they conducted a controlled explosion in the area.

US media reported that between seven and 20 people had been injured and that the suspected shooter may have been carrying a bomb. People at the club made similar reports on social media.

The incident comes less than a day after a gunman killed American singer Christina Grimmie after an Orlando concert. The assailant committed suicide after the act.

(DW)