A woman has been arrested after a security alert which put a US Army base into lockdown earlier.

Officials at Fort Lee in Virginia reported what they called a 'single shooter'. The woman has been described as 'disgruntled', and appears to have been injured.

The all clear was earlier given at the base after reports of an "active shooter".

The Pentagon said the shooter was female, that she was injured and was the only casualty.

Earlier in the day, police cars rushed to the scene. The base is about 40kms south of Richmond.

The four-storey building involved in the incident is the headquarters building for the base.

It houses the Combined Arms Support Command.

According to the military's website, Fort Lee is the third-largest training site in the Army, with a daily population of about 34,000, including members from all branches, their families, civilians and contractors.