
Islamic leaders have condemned the incident as "reckless and targeted", while WA Police are probing it as suspected criminal damage.
CCTV vision has been released of a hooded person climbing the fence of the Masjid Al-Rahman Mosque in Gosnells holding two large jerry cans.
While off camera, police say they poured the oil on the brick paving at the entrance on October 11 around 11.45pm.
The offender did not attempt to ignite the fluid, before they were later seen on video walking away holding the same cans and driving off in a white 4WD.
In a statement, the Council of Imams WA described the incident as "reckless and targeted", while posing a "hazardous and distressing" threat.
"It has understandably unsettled many within the community.
"We urge calm, unity, and trust in the investigation as police continue their work."

In a Facebook post, the Masjid Al-Rahman Mosque echoed the statement encouraging people to remain calm.
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"Let's remain calm, united and cooperative as we stand together for the safety and dignity of our community."
Specialist squad investigating
The incident is being investigated by the State Security Investigation Group — a division of the WA Police that deals with threats that are religious, racially or ideologically motivated.
Earlier this month, the dedicated squad charged a 36-year-old man with making multiple Nazi-gestures at a pub in East Perth.
In March, the same team of detectives charged a 16-year-old boy Bunbury boy for allegedly making violent threats online against a Sydney Mosque.
Earlier in the year, police increased their patrols outside synagogues following a spike in attacks over a 24 hour period.
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WA Premier Roger Cook said any attack on a religious institution was a concern.
"Western Australia is a great place to live, one of the reasons why it's a great place to live is because we're tolerant, we're inclusive and we're a united and safe community," he said.
"Everyone must do their best to ensure that we all do what we can to ensure that we maintain those values."
Police are urging anyone with information, CCTV or dash-cam footage to contact them.
Source: abc.net.au