An ancient Stonehenge-style stone in West Cornwall, U.K., has been defaced with "alien" graffiti.

On part of the Mulfra Quoit, a Neolithic structure that is more than 5,000 years old, one of the granite stones was likely graffitied with grey paint, according to Cheryl Straffon, a member of the Cornish Ancient Sites Protection Network.

"These figures have been painted on one of the uprights of Mulfra Quoit," Straffon said in comments posted to the groups' Facebook page. "Fortunately it is grey paint that can be removed, but one wonders at the mentality of people who will disrespect an ancient site in this way!"

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Several Facebook commenters expressed their dismay at the vandalism. "Disgracefull!!!" said one person, while another said the actions were "mindless and disgraceful." Other people have donated money to help with the clean-up efforts.

"We have reported this graffiti to Historic England, and they are discussing ways that it can be safely removed," Straffon told British news agency SWNS.

The site, which dates between 3500 to 2500 B.C., is the remains of a Neolithic dolmen, a type of megalithic tomb that likely had four large upright stones that supported a large horizontal capstone.

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