LOS ANGELES (AFP) - United States investigators are not ruling out terrorism as a motive for the Los Angeles airport shooting which Friday left a security agent dead, the Federal Bureau of Investigation (FBI) said.

An FBI statement confirmed that one person - a Transportation Security Administration (TSA) agent - was killed in the incident.

"It would be premature to comment on a motivation at this time and joint investigators have neither ruled out terrorism, nor ruled it in," it said.

The gunman opened fire with an assault rifle at LA international (LAX) airport shortly after 9am (12am, Saturday, Singapore time), killing the TSA agent and wounding seven people, officials said.

The shooter was reported to be in critical condition in hospital, according to the Los Angeles Times newspaper.

Panicked travelers scrambled to escape after the lone suspect, described by witnesses as a young white male, pulled out the gun and began shooting.

He went through a TSA checkpoint before doubling back into the main terminal area, where he was eventually stopped in an exchange of fire with police.

"The suspect was arrested following an officer-involved-shooting, the circumstances of which are also under investigation by police," said the FBI statement.