AN alert that warned of a ballistic missile heading straight for Hawaii and sent residents into a full-blown panic on Saturday was a mistake, officials have said.

The emergency alert, which was sent to mobile phones shortly after 8am, said in all caps: "Ballistic missile threat inbound to Hawaii. Seek immediate shelter. This is not a drill.".

The incident prompted defence agencies, including the Pentagon and the US Pacific Command, to issue the same statement: that they had "detected no ballistic missile threat to Hawaii".

The alert caused a furore on the island and across social media.

At the PGA golf tour event on Oahu, Waialae Country Club was largely empty and players were still a few hours from arriving.

Staff members at the club streamed into the clubhouse and tried to seek cover in the locker room, which was filled with the players' golf bags, but instead went into the kitchen

Justin Thomas, PGA Tour player of the year, tweeted: "To all that just received the warning along with me this morning ... apparently it was a 'mistake'?? hell of a mistake!! Haha glad to know we'll all be safe."

Hawaii US Senator Brian Schatz tweeted the false alarm was "totally inexcusable" and was caused by human error.