A man armed with a knife approached two 11-year-old girls and ordered them to follow him, police say.
The girls claimed the man pointed the knife at them before they ran away during the incident in Wincobank Woods in Sheffield.
No-one was injured during the incident.
South Yorkshire Police said the incident was "alarming" and that finding the man was a "priority".
The suspect is described as:
- in his early 20s
- having long ginger hair which was in a ponytail
- wearing a pale blue t-shirt which had drawings of female faces on
Anyone with information is 101 quoting incident number 891 of 26 June 2016.