Photo: The Canadian Press. All rights reserved.

A U.S. airman who helped subdue an attacker on a French train in August, was stabbed and is in stable condition in California, the Air Force says.

Spokesman, Lt. Col. Christopher Karns, said details are sketchy, but Spencer Stone is being treated in a hospital in the Sacramento area. The stabbing is being handled by local law enforcement officials, and Karns had no details on the nature or exact location of the stabbing.

Stone, 23, and two of his childhood friends from Sacramento, Alek Skarlatos and Anthony Sadler, stopped a gunman on a Paris-bound passenger train in August, receiving worldwide accolades and gaining sudden celebrity.

President Barack Obama met with the three last month, praising them for their quick thinking and courage and calling them "the very best of America." They previously had been awarded France's highest honour by President Francois Hollande.

The three have appeared on late-night talk shows and received a hometown parade in their honour since subduing the attacker while vacationing in Europe.

Stone, who has been acclaimed for his aggressive role in disarming the gunman, had undergone medical treatment at a military base in Germany for a lacerated thumb and other injuries he suffered in the attack. He is assigned to Travis Air Force Base in California.

Skarlatos is scheduled to appear on ABC television's "Dancing with the Stars," which he was rehearsing for when a gunman killed nine people at the Oregon community college he attends last week.