An artwork by Banksy that has attracted hundreds of visitors a day to Port Talbot in south Wales was targeted on Saturday night by someone who tried to pull down fencing erected to protect it, according to a local report.

Gary Owen, a local man who claims to have effectively commissioned the anonymous artist in an Instagram message suggesting a work protesting against pollution from the local steelworks, said the attacker was chased away without causing any damage to the painting, which wraps around the corner of a residential garage.

“Some drunk halfwit has tried to pull the fencing down and the protection glazing at the Banksy artwork tonight,” Owen wrote on his Facebook page. “The security guard chased him off and police were called. This art is for Port Talbot, Neath and surrounding areas. We do not want it wrecked.”

The artwork, which appeared earlier this week, depicts an open-mouthed child letting flakes of what appear to be snow falling on their tongue, but which is in fact ash from a fire in a large bin. A local businessman has erected a screen across part of the mural and the actor Michael Sheen, who comes from Port Talbot, is paying for the security guard to protect it.

The local council has stationed members of staff on nearby roads to help manage traffic, as the mural has attracted thousands of visitors, according to Anthony Taylor, a local councillor.

“There are always 40 to 50 around it,” he said. “People are there at all times of day. We are delighted to have the attraction but we have asked for there to be a little bit of respect. We are trying to get to grips with it, and in the new year we will try to organise things a bit better.”

Owen said he had sent a message to Banks via Instagram, which read: “Can you do some art in Port Talbot? The steelworks is making lots of dust every day and the locals are sick of it. …Seagulls with gas masks comes to mind ... lol”.

Previous Banksy artworks on buildings have been screened off and even dismantled and sold.

The reported attempt to breach the screen in Port Talbot was not universally condemned. One person commenting on reports on Facebook said, in reference to a stunt in which a £1m painting was shredded as soon as it was sold, said: “Hang on ... didn’t he destroy his own recently, at a Sotheby auction? Double standards?”