The design - featuring a school of swimming fish - differs from the artist's characteristic silhouette artworks, and it has yet to be claimed.

It appeared on a police box in the City of London.

If confirmed, it would be his seventh artwork to be unveiled this week in various locations across the capital.

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The new design has been examined by two City of London police officers, PA news agency reports, who took pictures from the outside of the police box.

One officer said they were asked to check out the artwork after it was picked up on CCTV cameras and that they are waiting to hear what will be done about it.

Recent artwork has included a goat, elephants, monkeys, a wolf, pelicans and a cat.

On Saturday, a piece of a stretching cat on an empty, distressed advertising billboard was removed from its location in northwest London hours after it was revealed.

A day earlier, another mural appeared above a fish and chip shop in the northeast of the capital.

The picture was a silhouette of two pelicans, one eating a fish, drawn above the Bonners Fish Bar in Walthamstow.

According to the Guardian, the new series of work by the elusive artist is meant to cheer up the public at a time when the news has been bleak, including headlines on widespread rioting across England.

Banksy usually leaves months between his artworks, confirming them soon after they appear on social media.

With one posted every day so far this week, there has been much speculation about the meaning behind the animals, but he has not captioned any of the photos shared on Instagram, adding to the mystery.

The Bristol-based anonymous artist made headlines in June when he released a migrant boat installation over the crowd at Glastonbury during performances by Idles and Little Simz.

He was behind another artwork discovered on the side of a block of flats near Finsbury Park, north London, and subsequently vandalised in March.

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