Barriers have been put up around Banksy’s latest artwork of piranhas swimming on a City of London police sentry box after the street artist confirmed it as his piece.

The glass-paned box – which has been painted with what appears to be translucent spray paint to turn it into what looks like a giant fish tank – is located on Ludgate Hill near the Old Bailey court.

After Banksy claimed the piece on Instagram on Sunday, the governing body of the City of London said it is working on options to “preserve” the new artwork.

It marks the seventh animal-themed design the Bristol-based artist has revealed in London this week since Monday.

The new artwork differs from Banksy’s previous dark silhouette images of a goat, elephants, monkeys, a wolf, pelicans and a cat which have popped up in various locations across the capital.

After it appeared, City of London police officers turned up to examine the piece and the force said it was liaising with the City of London Corporation on what should be done with the artwork.

In a statement to the PA news agency, Detective Chief Inspector Andy Spooner, for the City of London Police, said: “We are aware of criminal damage to a City of London Police box in Ludgate Hill. We are liaising with the City of London Corporation who own the police box.”

A small crowd gathered to see the piece after it was confirmed to be a genuine Banksy while police officers kept watch.

Plastic barriers were later erected around the box by a worker from the City of London, preventing people from posing for pictures inside the artwork.

A City of London Corporation spokesperson said in a statement to PA: “We’re aware of the works on the City of London police box on Ludgate Hill.

“We are currently working through options to preserve the artwork.”

Among those who came to see the new artwork was photographer Avi Yasitli, 63, who has been to see all of the new Banksy pieces of art this week except one piece which was taken.

He said he thinks the animals are a message from the artist that the city has “turned into a zoo”.

Artist Daniel Lloyd-Morgan, who has painted most of Banksy’s pieces of art this week, said the new collection is “really uplifting for people in London at the moment”.

“There’s a buzz around his work. It’s nice to capture that as I do the people as well”, he added.

“It’s not just about the artwork, it’s about the whole environment he’s creating, it becomes a sort of work of art itself – what happens to it, people steal it or take it away.”

A local resident also said she had walked up the road yesterday and did not recall seeing it there but thought the new addition had “charm”.

It comes after the artist’s sixth piece – a stretching cat on an empty, distressed advertising billboard – was removed from its location in north-west London hours after it was revealed on Saturday.

Crowds booed as the piece in Cricklewood was dismantled by three men who said they were “hired” by a “contracting company” to take down the billboard for safety reasons.

A contractor, who only wanted to give his name as Marc, told PA they were going to take the board down on Monday and replace it, but the removal had been brought forward to Saturday in case someone “rips it down and leaves it unsafe”.

An officer at the scene told PA that the owner of the billboard has told police he will donate it to an art gallery.

The cat design was the second piece to be removed during the week after a painting of a howling wolf on a satellite dish was taken off the roof of a shop in Peckham, south London, less than an hour after it was unveiled.

It was removed by three men, according to a witness, who told PA that he filmed them, which led to one of the men throwing his phone on a roof.

A spokesman for Banksy told PA that the artist is neither connected to nor endorses the theft of the wolf design and that they have “no knowledge as to the dish’s current whereabouts”.

The first piece of graffiti in Banksy’s new animal-themed series, which was announced on Monday, is near Kew Bridge in south-west London and shows a goat with rocks falling down below it, just above where a CCTV camera is pointed.

On Tuesday, the artist added silhouettes of two elephants with their trunks stretched towards each other on the side of a building in the Chelsea area of west London.

This was followed by three monkeys looking as though they were swinging underneath a bridge over Brick Lane, near a vintage clothing shop in the popular east London market street, not far from Shoreditch High Street.

The fifth design, of pelicans pinching fish from a London chip shop sign in Walthamstow, east London, was revealed on Friday.