US police announced that a 6-year-old boy shot and injured a teacher - yesterday, Friday - at an elementary school in Newport News, Virginia.

Police Chief Steve Drew told reporters that the injury to the teacher, who is in her 30s, posed a threat to her life, although she showed some improvement in hospital.

There was no further explanation as to how the 6-year-old had obtained the gun.

Police described the incident as a "brawl" in the front row room, which resulted in one shot being fired.

"This was not an accidental shooting," Drew said, later adding, "I want to know where that firearm came from."

Drew said the child was taken into custody, and no students were injured in the incident.

At the same press conference, headmaster George Parker lamented the inability of teachers to prevent firearms from entering schools, and said he was "shocked" and "disappointed".

"We need guns not to get into the hands of our young people," Parker said. "I can't control access to guns, and teachers can't control access to guns."

The headmaster explained that all schools are equipped with metal detectors, but they were not activated at Retnik Primary School on Friday.