A policeman who allegedly placed a rope across a pathway, causing two teenage boys on a motorcycle to fall off and suffer injuries, has faced a Perth court on assault charges.

Matthew Gerard Owen Pow, 38, was off duty on November 27 when he allegedly placed the rope across a pathway at a park in Karawara in Perth's south.

Two boys, aged 15 and 16, struck the rope with the motorcycle and were injured when they fell off their bike.

Pow appeared in the Perth Magistrates Court today, charged with two counts of assault occasioning bodily harm and one count of an act or omission causing grievous bodily harm or danger.

He is a senior constable from the Specialist Enforcement and Operation Portfolio but was stood down after the charges were laid.

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Pow will reappear in court on March 31.

AAP