The shooting, which took place at Naval Air Station Pensacola in Florida, left seven people injured including two sheriff's deputies who responded to the attack, one of whom was shot in the knee, the other in the arm.

Police received their first call about the shooting shortly before 7:00 am (1200 GMT), Escambia County Sheriff David Morgan told a press conference. One of the responding deputies eventually killed the attacker.

"Walking through the crime scene was like being on the set of a movie," Morgan said. "You don't expect this to happen at home."

Police declined to identify the shooter or whether or not they were in the military. They also would not say if they thought the act was motivated by terrorism.

Commanding officer Timothy Kinsella said the base's security forces first responded to the shooting before outside police agencies arrived.

The facility, which is used for training and made up mostly of classrooms, "is shut down until further notice," he said.

Witnesses to the shooting described a chaotic scene as police rushed to respond.

"There's probably been 100 or so various law enforcement vehicles" driving through opposing traffic towards the base, Jeff Bergosh, a county commissioner who is a contractor at the facility, told the Pensacola News Journal newspaper.

White House press secretary Judd Deere said President Donald Trump "has been briefed on the shooting at Pensacola Naval Air Station... and is monitoring the situation."

Broadcaster WEAR showed footage of an injured person being wheeled into a hospital.

Federal agencies are investigating, authorities said, including the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Just two days prior on Wednesday, a US sailor fatally shot two people and wounded a third at the Pearl Harbor Naval Shipyard in Hawaii before taking his own life.

- Military rarely targeted -

The Pensacola naval air station hosts 16,000 military personnel and more than 7,000 civilians, and is home to a flight demonstration squadron.

It is an early training center for naval pilots, and is known as the "cradle of Naval aviation."

While mass shootings in the United States are common, those at military facilities are rare.

In July 2015, Mohammad Youssuf Abdulazeez carried out an attack at two military installations in Tennessee that killed four Marines and a sailor, with the FBI concluding that the violence was inspired by a "foreign terrorist group."

Two years earlier, Aaron Alexis killed 12 people and wounded eight others at the Washington Navy Yard, just two miles (three kilometers) from the US Capitol building, before being shot dead by officers.

Four years before that, Major Nidal Hasan, a US Army psychiatrist, killed 13 people and wounded more than 30 others at Fort Hood.

He was considered a "lone wolf" who supported terror network Al-Qaeda.

Supporters of tighter gun laws seized on the latest shooting.

"Our veterans and active-duty military put their lives on the line to protect us overseas -- they shouldn't have to be terrorized by gun violence at home," Cindy Martin, a volunteer with the Florida chapter of Moms Demand Action whose daughter works at the naval base, said in a statement.