WA Premier Mark McGowan announces security increase after attack on office

West Australia Premier Mark McGowan has announced that his office will beef up security in the lead up to Saturday's election, after a package containing a "powder substance" was hurled at this office yesterday.

"In terms of security, it's a very heightened environment, naturally I think there is an increase of security," Mr McGowan said today.

READ MORE: Driver provides fake details after allegedly hitting six-year-old boy

"I'm not worried at all, I'm not concerned. West Australians are terrific, these are very odd isolated cases.

"It was some sort of foil package, it was some sort of powder or something of that nature, that caused concern. It's being tested and checked for any chemical residue."

The man allegedly responsible for throwing the package was arrested yesterday.

He allegedly flung the object toward staff at the premier's office in Rockingham at about 4pm local time yesterday and then fled the scene.

The package has since been confirmed by police as containing a "water based substance".

"A man ran into the office, he chucked a package under the security screen and then he ran out," Mr McGowan said.

READ MORE: WA Premier Mark McGowan's proposal for post-COVID border control sparks backlash

The office was immediately evacuated and one staff member was taken to hospital as a precaution.

A similar package was also discovered at the electorate office of federal MP Madeleine King, with the office also evacuated.

Neither Ms King or Mr McGowan were in the area at the time, but staff were left shaken.

Mr McGowan said he has been in contact with his staff who were present at the time and they are "pretty upbeat".

Western Australia is set to head to the polls on Saturday, for a state election Mr McGowan's Labor is expected to overwhelmingly win.

The attack on Mr McGowan's office follows a death threat the day prior, when a man at a Perth early polling booth told people he had a gun and he planned to shoot the premier.

A major Labor billboard was also graffitied in Nazi symbolism.

Police are investigating the incidents.