SHOOTING CHAOS: One dead as gunman opens fire at airport

A GUNMAN with a semi-automatic weapon has shot three people, killing a federal security agent, at the Los Angeles airport, US police say.

One person is critical and two others in a ''fair condition'', a hospital spokeswoman told the media.

Flights have been disrupted across the United States.

Police chief Patrick Gannon said a lone gunman walked into Terminal 3 at LAX at 9:20am and proceeded to pull an assault rifle out of a bag and began shooting.  He then walked through the airport and into the screening area and again opened fire.

Mr Gannon said police were engaged in a shootout with the gunman who was shot and taken into custody.

In this photo provided by John Forstrom, which has been authenticated based on its contents and other AP reporting, people wait at Gate 142 in Los Angeles Inteational Airport, Friday, Nov. 1, 2013. Shots were fired Friday at Los Angeles Inteational Airport, prompting authorities to evacuate a terminal and stop flights headed for the city from taking off from other airports.(AP Photo/John Forstrom)

The airport was being swept for precautionary measures, and the bomb unit was on scene.

Tim Kauffman, a spokesman for the American Federation of Govement Employees, confirmed that a Transportation Security Administration officer was killed.

He said the union's information came from their local officials in Los Angeles.

Mr Gannon said seven people required medical attention and that six had been taken to hospital.

Ronald Reagan UCLA Medical Center said it received "three male victims from the LAX Airport shootings. One arrived in critical condition and two are listed in fair condition".

The gunshots were reported at Terminal 3.  Qantas, Virgin Australia, United and Delta all use the airport for Australian flights.

Passengers evacuate the Los Angeles Inteational Airport on Friday Nov. 1, 2013, after shots were fired there, prompting authorities to evacuate a terminal and stop flights headed for the city from taking off from other airports. (AP Photo/Ringo H.W. Chiu)

Virgin Australia uses terminal three, where the shootings occurred.

Air traffic was affected across the country as the Federal Aviation Administration grounded flights that had not yet departed for LAX.

Witness Brian Keech said he heard "about a dozen gunshots" from inside a security gate at the terminal.

LAX air traffic controller Michael Foote said his colleagues in the control tower saw passengers spilling from the terminal on to the tarmac, "evacuating the building, getting out as fast as they could".

Other travellers described a chaotic scene as airport security staff evacuated terminals.

Hundreds of people remained gathered outside next to planes.

Police walk outside Terminal 3 at Los Angeles Inteational Airport on Friday, Nov. 1, 2013. Shots were fired Friday at Los Angeles Inteational Airport, prompting authorities to evacuate a terminal and stop flights headed for the city from taking off from other airports. (AP Photo/Ringo H.W. Chiu)

"People started saying there's a shooter, there's a shooter," said Natalie Morin, who was heading to San Francisco for a graduate school interview.

TV footage showed one person on a guey, being loaded into an ambulance. Another victim was seen being rushed away on a wheelchair.

Tory Belleci who hosts the US television show Mythbusters tweeted: "Heard gun shots then everyone starting running for the door. Not sure if anyone was hurt. #LAX."

We are being shuttled away from the terminal now. Eye witness said the shooter had an assault riffle. pic.twitter.com/euFxdEo0z7 — Tory Belleci (@ToryBelleci) November 1, 2013

Police stand outside Los Angeles Inteational Airport on Friday, Nov. 1, 2013. Shots were fired Friday at Los Angeles Inteational Airport, prompting authorities to evacuate a terminal and stop flights headed for the city from taking off from other airports. (AP Photo/Reed Saxon)

Hundreds of travellers could be seen streaming away from at least one terminal building, while multiple ambulances and emergency vehicles rushed to the scene.

Other passengers lined up on the tarmac near an aircraft, as officials scrambled to manage flights and travellers amid the unfolding incident.

US President Barack Obama has been briefed on the shooting, the White House said in a statement.

"We will continue [to] stay in touch with our federal and local partners," a White House official said in a statement. "The LAPD is leading the response and investigation. We urge citizens to listen to the authorities and follow directions from the first responders on site. The president will continue to receive briefings throughout the day."

In 2002, an Egyptian national opened fire at LAX, killing two Israelis before he was shot dead. Authorities ruled it a terrorist incident, even though the shooter was not tied to a known group.

LAX served about 64 million fliers last year. More than 1500 flights take off and land there every day.