WOOD chippings underneath a children’s climbing frame were set alight.
Firefighters were called to Cosham Park, Portsmouth, shortly after 6.20am on Saturday.
Two buckets of water were used to put out the flames.
A passer-by made the 999 call but they were not around when crews turned up. Crew manager Lawrence Mackrell said: ‘We recorded it (the incident) down as malicious.’