A man has died after shots were fired at at the US city of Houston's largest airport, prompting a security lockdown and the suspension of some flights.

Roxanne Mena, spokeswoman for the Harris County Institute of Forensic Sciences, confirmed the shooting death on Thursday at the Bush Intercontinental Airport in the US state of Texas.

There were no other injuries or suspects involved in the shooting, Houston police spokeswoman Jodi Silva said. The dead man was not identified.

According to another police spokesman, the man fired at least one shot at the ceiling. He was then confronted by a Homeland Security officer nearby, who fired his weapon.

The man treated by responding paramedics, but was later pronounced dead in an ambulance.

It was not clear if the man died from a self-inflicted gunshot or from one or more shots fired by the security officer.

Parts of airport, named after President George H.W. Bush, remained blocked off as police investigated the shooting.

The airport announced on its Twitter feed that the terminal had been closed and passengers would be redirected to other terminals.

A witness, Dale Howard, was at the baggage handling area of the airport waiting for his sister to arrive on an incoming flight when he heard two shots fired from the floor above. A few seconds later, he said he heard three more shots.

"People were screaming. I knew exactly what it was - gunfire,'' Howard said.

Other witnesses said people ran and dived for cover during the shooting at one of the nation's busiest airports.

The shooting happened just a day before the National Rifle Association begins its annual conference in Houston. Thousands of advocates for the right to bear arms are expected to attend.

Source: Agencies