American Ryder Cup players Dustin Johnson and Zach Johnson have pulled out of this week's Ballantine's Championship in South Korea.

A statement from the tournament sponsors said the two players had reached their decision due to "perceived unrest" on the Korean peninsula, but stressed that the event was going ahead as planned.

The statement read: "Ballantine's is disappointed to announce that Dustin Johnson and Zach Johnson have informed us they will no longer be attending the Ballantine's Championship.

"They have reached this decision following perceived unrest on the Korean Peninsula and can no longer assure their commitment to this year's event.

"Ballantine's can, however, confirm a list of world-class players attending the Ballantine's Championship, including Louis Oosthuizen, YE Yang, Bae Sang Moon, Paul Lawrie, Thomas Bjorn, Thongchai Jaidee, Marcus Fraser and Paul Casey.

"Ballantine's and event organisers, the European Tour, would like to reiterate that the tournament is going ahead as planned with a full field of European, Asian and Korean PGA Tour members.

"Ballantine's has been kept fully up to date on relevant issues and the European Tour has also been liaising with key decision makers, including the Foreign Office, who have not warned of any increased risk to those travelling to or within the country.