Two girls were playing in a park in Northamptonshire when a man exposed himself.
The offender, who is believed to be white and in his 30s, approached the girls, aged eight and 10 who were playing in Queensway Park in Wellingborough.
The man exposed himself to them, at which point the girls ran away.
The incident happened between 2.30pm and 3pm on Wednesday, February 18.
Officers are appealing for witnesses or anyone with any information to call Northamptonshire Police on 101.
Alternatively, they can call the independent charity Crimestoppers anonymously on 0800 555 111 or use the anonymous online form at www.crimestoppers-uk.org.