Police have released a photo-fit of a man they wish to speak to after 12-year-old girls were told to expose themselves at a playground in Melbourne's north-east.

The three girls were approached by the man as they played in the Halle Supple Reserve playground at about 4.45pm on Thursday, August 2.

The group left immediately and later reported the incident to police.

The culprit is described as being in his late 30s or early 40s, solid build and balding with red hair and a moustache.

He was wearing a white polo shirt and jeans.