Police are asking the public to keep an eye out for a male who matches this description; particularly the man's clothing, as the physical description is quite general.
"The two girls did the right thing by immediately reporting the incident to a trusted adult, who then contacted police," said Sergeant Jayne Ross.
"We take reports of this type of behaviour very seriously and have increased patrols in the area as we continue to make inquiries."
Any sightings or information can be reported to Johnsonville Police on 04 381 2000 or email Johnsonville.cpc@police.govt.nz.
Ross said people calling police with information about this matter should quote case number 170402/0732.