Electoral banners were ripped by vandals.
Cassola said the banners had replaced others that had been stolen a few days previously.
A police report has been filed.
Cassola said these continuous attempts to silence him would not work. "I am committed to continue passing on my positive message in favour of residents and the environment while challenging the arrogance of bullies and cowards who are destroying our country," he said.
PN candidate Peter Agius also complained about vandalism on his banners in Gozo a few days previously.