Orlando shooting: Islamic State claims responsibility for nightclub attack, says Omar Mateen was 'soldier of the caliphate'

Washington: In a major development in Orlando shooting incident, Islamic State (IS) terrorist group has claimed the responsibility for the attack.

In a message published on the group’s semi-official news agency, Amaq, it described gunman Omar Mateen as a “soldier of the caliphate”.

Worst mass shooting in US history

In the worst mass shooting in US history, at least 50 people were killed and 53 others injured when a "lone wolf" gunman opened fire early on Sunday in a gay nightclub in Orlando, Florida. 

Although the statement did not clarify Mateen’s relation to the group, but the language appeared to suggest he was viewed as a lone wolf attacker.

A state of emergency has been declared in Florida.

Gunman Omar Mateen

The gunman Omar Mateen, 29, was killed by a SWAT team after he took hostages at Pulse, a popular gay night club. 

He was armed with an assault rifle, a handgun and an unspecified "device", said officials.

"It appears he was organised and well-prepared," Orlando Police Chief John Mina said.

Officials said the killings were likely to be ideologically motivated, though there was no information that the gunman was associated with a particular group.