An artwork of swimming fish painted on to a City of London Police sentry box has led to speculation it may be the latest in a new series of works from the artist Banksy.

The glass-fronted box on Ludgate Hill has been transformed to look like an aquarium.

The elusive street artist from Bristol has not yet confirmed he is behind the creation, but if he does, it would be his seventh new artwork to be revealed in the capital in as many days.

Since Monday, stencilled silhouette images of a goat, elephants, monkeys, a wolf, pelicans and a cat have popped up in various locations across London.

The sentry box is a short distance from landmarks such as the Old Bailey and St Paul’s Cathedral.

Two City of London Police officers have visited the sentry box and taken pictures.

One officer said the art was picked up on CCTV cameras and they were asked to come and have a look.

He added that they were waiting to hear what will be done about it.

The work differs from the previous works by Banksy unveiled this week in that it is a detailed painting that appears to have been created with translucent spray paint.

A City of London worker who came to look at the fish artwork said he did not think it was a Banksy.

The man, who did not wish to be named, said: “I’m not too sure if it is Banksy. It’s not his style.

“I prefer the other ones he has done because they are on buildings.

“But this, I don’t know, I don’t think it’s him.”

On Saturday, 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.

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.

Hours after Banksy confirmed the design was his, crowds gathered from across London to see the piece before the men, who claimed to be contractors, arrived.

A black board was first used to cover up the cat artwork on the billboard at the request of the police, who wanted to stop people walking in the road in front of traffic.

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.

The artist has been making announcements on his Instagram page claiming the works each day since Monday.