WASHINGTON - THE FBI said on Tuesday the same weapon was used in shootings at the Pentagon and a US Marine Corps museum in Virginia this month, with a third incident also possibly linked.

Federal authorities are investigating whether a third shooting that took place overnight at a Marine Corps recruiting station in Chantilly, Virginia involved the same gun, the FBI said in a statement.

No one was injured in the Oct 17 shooting at the National Museum of the Marine Corps outside its Quantico base in Virginia, south of Washington, or at the Pentagon two days later.

In the Pentagon incident, at least six gunshots struck the sprawling Defence Department headquarters and broke two windows, prompting police to briefly close the building. No suspect was found and police suspected the shooter had used a high-velocity rifle.

The Federal Bureau of Investigation said 'evidence has confirmed that shots fired at the National Museum of the Marine Corps... and the Pentagon... involved a single weapon.'

The FBI has opened a probe into all three shootings and said it was carrying out 'ballistics testing' for the incident at the recruiting office in Chantilly that occurred some time between late Monday and early Tuesday.

FBI links 2 shootings