PARTS of a playground was damaged when a lighter was thrown into the area.
The lighter set fire to bundles of hay and tyres that made up part of Stamshaw Adventure Playground, in Western Terrace.
One crew from Southsea were called at 4pm and put out the blaze.
Hampshire police believe the fire was started deliberately.
A spokesman said: ‘We believe a lighter was used and we’re treating it as arson.’