British holidaymakers in Orlando, Florida, have been urged to stay away from the area around a gay nightclub where 50 were killed in a terrorist massacre.

Besides the multiple killings in the early hours of Sunday morning, attacker Omar Mateen wounded 53 at the Pulse club before being shot dead by police.

The so-called Islamic State group has said it was behind the attack – the worst mass shooting in recent US history – but the extent of its involvement is not clear, the BBC reported.

States of emergency were declared in the city of Orlando and surrounding Orange County.

The Foreign and Commonwealth Office acknowledged the incident in updated travel advice and said: “You should avoid the area if possible and follow the advice of the local authorities.”

US president Barack Obama described the gun attack as “an act of terror and an act of hate”.