A Perth woman has expressed concern about the possibility of radicals attempting to recruit extremists to the Syrian conflict after witnessing a "Die for Syria!" sticker on a car in Southern River.

Sharon, who did not want her surname published, said she was dumbfounded to see the slogan on the back windscreen of a Mitsubishi in Warton Rd last week.

The car displaying the DIE FOR SYRIA! sticker.

She is worried the car's owner may be attempting to incite violence or recruit extremists to the Middle East conflict.

"I was in total disbelief. I just couldn't believe what was in front of me," Sharon told radio 6PR Drive host Paul Murray on Wednesday.