The foul call on Lonzo Ball at the end of regulation should not have resulted in three free throws, an NBA referee has admitted.

NBA referee Tom Washington conceded officials were wrong to award the Oklahoma City Thunder three free throws following Lonzo Ball's late foul after LeBron James had criticised the initial decision.

With his team winning 122-119 with less than five seconds to play, Lakers guard Ball reached in and fouled Thunder star Russell Westbrook.

The referees ruled Westbrook was in the shooting motion, which gave him three free throws.

Westbrook made all three shots, sending the game to overtime, with the Lakers going on to win the game 138-128.

However, Washington explained afterwards that the call on Ball was wrong.

"The official called the foul because at the time he thought Russell had started his shooting motion and he was clearly behind the three-point line and there was illegal contact by Ball," he explained.

"There is not a trigger to review whether or not there is a foul prior to or on the shot.

"The trigger would be whether or not it is a three-point shot or not. And upon being able to see the review of the play, we realised that the illegal contact actually happened prior to his upward motion, so it should have been a side-out."

James had expressed his disbelief at the call on Twitter.

"So what really is 'in the shooting motion' rule?!?!?" James asked. "Asking for a friend @OfficialNBARefs."