Approximately 10,000 spectators a day will be allowed on site for this year's US PGA Championship, tournament organisers have announced.

Collin Morikawa will defend his title at Kiawah Island in South Carolina from May 20-23.

Face coverings will be required for all spectators, staff and volunteers, including those who have received a Covid-19 vaccine, and should be worn at all times, the PGA of America said.

"We're excited to welcome spectators back to the PGA Championship this May in a way that is responsible and aligned with current South Carolina health protocols," PGA of America president Jim Richerson said.

"While we wish we could accommodate the sell-out crowds who had purchased tickets, the 2021 PGA Championship will be steeped in gratitude as the best players in the world compete on the historic Ocean Course at Kiawah Island Golf Resort.

"While crowds will be smaller than originally planned, we know the passion for golf in the Carolinas will create a memorable atmosphere on course and excitement throughout the region."

The limited number of tickets will be allocated based on a combination of factors, including the purchaser's original registration group and time of purchase. Spectators who are unable to attend will be given a refund.

Rory McIlroy won the last major to be staged at Kiawah Island, the Northern Irishman claiming an eight-shot victory in the 2012 US PGA.

April's Masters is also set to go ahead in front of a "limited number" of spectators, although officials at Augusta National have not given a specific number.