Six cyclists are in a critical condition after being hit by a truck in Arizona, with the driver chased down and shot by police.

It happened at about 7.25am local time in the town of Show Low, northeast of Phoenix, during an organised bicycle race.

Police said four people were in a critical condition and that two were critical but stable.

Officers pursued the driver, who fled the scene, and shot him behind a hardware store. The suspect is critical but stable.

There were also two to three walk-in victims, police added.