American football star Adrian Peterson is keeping a bedside vigil after his two-year-old son was rushed to hospital in a critical condition.

The boy is currently under doctors' care at a medical centre in South Dakota with severe head injuries after an alleged assault.

Emergency crews were called to an apartment on Wednesday evening (09Oct13) where the boy was unconscious, and he was taken to a nearby hospital. Minnesota Vikings star Peterson is at his son's bedside.

Police have charged a 27-year-old man with aggravated felony assault and battery of an infant, according to Tmz.com.