TWO Perth teenagers have been charged over allegedly using a toy gun to fake a series of armed robberies and filming the incidents to later post on YouTube.

Police allege the youths, aged 13 and 16, faked the armed robberies at a fast food restaurant, a pharmacy and a supermarket in Warnbro, in Perth's south, on Thursday afternoon between 3.30pm and 3.45pm (WST).

In each store, one of the youths used a toy firearm to make demands to staff while the second teenager recorded the incidents on a mobile phone, police said.

"Members of the public are being subjected to a harrowing experience... to make their social networking pages more appealing."

They left each store before staff could comply with any demands.

Police say they believe the youths planned to post the recordings on YouTube.

Inspector Paul McMurtrie said the behaviour from the teenagers was "totally unacceptable" and was a serious criminal offence.

"What is of serious concern is innocent members of the public are being subjected to a harrowing experience in order for some misguided youths to make their social networking pages more appealing," he said.

"The victims are unaware that they are the brunt of a prank and may experience the same levels of anxiety and stress as in a real event."

The youths have been charged with being armed in a way that may cause fear.

They will appear in the Rockingham Children's Court on August 31.

Originally published as 'Teens faked gun robberies for YouTube'