Three corbelled stone huts at ix-Xagħra l-Ħamra in Mellieħa have been vandalised.
These old rural structures (ġiren) are abundant in this area, with more than 30 located within the park itself.
Majjistral Nature and History Park, together with a number of environmental NGOs, issued a joint statement to condemn the attack.
This is not the first time vandals have targeted the park. Various interpretation signs were destroyed as soon as they were erected in the area last year.
The organisations appealed to the public to report any suspicious activities to the police.