Five Muslim graves were vandalised last weekend at the Intiö cemetery in Oulu. Three of the graves belonged to the Somali-background boys who drowned at Kalajoki's Hiekkasärkät beach last summer.
Vandals spraypainted the graves with black paint. The local parish filed a police report earlier this week.
Sanna-Kaisa Rivasto, director of burial services, said the parish had contacted the reception home where the boys had lived, which served as their home in Finland.
She strongly condemned the vandalism.
"This is deeply reprehensible, and it has been very distressing to inform those affected," Rivasto said.
The incident was first reported by Iltalehti.
The boys' deaths last July sparked a debate about water safety after it emerged that there was no lifeguard supervision at the beach.
An accident investigation by the regional rescue service later concluded that the boys could not have been saved even if additional personnel had been dispatched to the scene.
