That's the equivalent of around 8,300 cases per year, according to the study in the Journal of the American Medical Association (JAMA) Pediatrics.

The number of youths wounded by gunfire declined in the first years of the study, then rose from 2013 to 2014. Most the casualties were boys aged 15-17.

Researchers found that about 11 under 18s per 100,000 were sent to emergency rooms due to gunshot wounds.

Half of cases were linked to a dispute of some kind, while 39 percent were accidents and two percent were suicides.

One third were hospitalized, and six percent were killed.