Two motorbike riders have died in an accident at a MotoAmerica Superbike/Superstock 1000 race in California.

Sunday's MotoAmerica Superbike/Superstock 1000 race in California was marred by tragedy as two riders died as a result of their injuries following a crash.

Bernat Martinez and Daniel Rivas Fernandez, both of Spain, were involved in the collision and were unable to recover in hospital.

"A chain-reaction, multi-bike incident on the first lap of the second MotoAmerica Superbike/Superstock 1000 race at Mazda Raceway Laguna Seca has resulted in the deaths of two competitors," a statement on MotoAmerica's official website read.

"Bernat Martinez, of Alberic, Valencia, Spain, was transported from the raceway by ambulance to Community Hospital of the Monterey Peninsula in Monterey, where he succumbed to his injuries. He was 35.

"Daniel Rivas Fernandez, of Moana Galicia, Spain, was transported by REACH Medical Air Services to Natividad Medical Center in Salinas, where he also succumbed to injuries. He was 27."

MotoAmericapresident Wayne Rainey said: "I really don't have any words to describe what we all feel.

"First and foremost, is the loss to the families and loved ones. Our sincere condolences go out to each and every one of them as well as the MotoAmerica family. They are in our thoughts and prayers."

Gill Campbell, CEO and general manager of Mazda Raceway Laguna Seca, added: "We are deeply saddened to learn the news of the passing of Bernat Martinez and Daniel Rivas. Our prayers and hearts go out to their families and teams."