A mass shooting at a crowded bar on an idyllic US island has left four people dead and at least 20 injured, officials say.

The shooting occurred early on Sunday (late on Sunday AEDT) at Willie’s Bar and Grill on St Helena Island in South Carolina, officials said.

A large crowd was at the scene when sheriff’s deputies arrived and found several people suffering from gunshot wounds.

“Numerous victims and onlookers hurried to nearby shops and buildings to find refuge from the gunfire,” stated the Beaufort County Sheriff’s Office in an announcement on the social media site X.

“This is a heartbreaking and challenging event for everyone involved. We request your patience as we continue to examine this situation. Our sympathies are with all affected individuals and their families.”

Four individuals were discovered deceased at the location, and over 20 others suffered injuries. Of those injured, four are in critical condition at local hospitals.

The victims’ identities were not released.