A Perth man accused of acting suspiciously around children at fast food outlets has been charged with a string of child sex offences.

Niaz Ahmed Ali, 58, was arrested on February 8 after police released images of a man sitting inside numerous fast food restaurants in Perth's southern suburbs appearing to conceal a recording device.

Police released this image to the public as part of their investigation.

The public appeal and a mobile police facility set up at a Baldivis park on February 4 assisted police to identify the man.

"It will be alleged between 2014 and 2016 the man frequented various fast food outlets, park playground areas and shopping centres across suburbs in the South Metropolitan and South East Metropolitan policing district," a police spokeswoman said.