The Għajn Żnuber tower was defaced with black oil during Friday’s stormy night, a day after CCTV watching over the historic building was stolen. 

In a video posted by the HPF Ranger Unit on Facebook, the damage to the site is seen extending to the surrounding area as the black liquid trails over the stones and dirt around the tower.

"Used engine oil has been used," an HPF Ranger Unit spokesperson said.

Also known as Ta' Ciantar farmhouse or Ta' Torri Ciantar, the area in Mellieħa has been closed off by rangers who asked to relay any information to the police.

The act of vandalism could have been pre-meditated.

On Thursday morning, the ranger unit reported that the CCTV monitoring the tower had been cut down and the camera stolen.

A spokesperson for the HPF Ranger Unit said the loss of the camera coupled with the extreme weather in which the vandalism occurred may point to a pre-planned act.

In 2012, restorations began for the tower, which saw it being transformed from a crippled lookout post to what it is today.

The structure is believed to have been built in the late 19th century. It was last used during the Second World War as a lookout post. After the war, the tower was abandoned and suffered from neglect and vandalism.