Early reports indicate gunshots were heard outside the security checkpoint at about 1.30 pm.
The airport was quickly evacuated.
According to the reports, there was a single shooter who has been arrested, and no injuries have been reported.
A video from the airport shows police detaining a man as travellers look on from other sections of the terminal, WA Today reported.
Travellers reported on social media the airport was placed into lockdown and there is a heavy police presence.
Airline staff are telling people who have arrived to collect passengers that anyone who was on a plane when the building was evacuated is being kept on the plane.
A spokesperson for the airport declined to comment, noting it was a “police matter at the moment”.
ZZ/PR