One goat, two elephants, and now three monkeys: British street artist Banksy thrilled fans in London on Wednesday by installing his third new artwork in three days.

The animal-themed collection has sparked speculation about their message. Are they criticism of England's far-right riots or possibly support for Palestinians? Perhaps they reference global warming or even the Olympics?

As usual, the enigmatic artist gave no explanation when he claimed them on Instagram. What is unusual is how quickly they have appeared -- usually Banksy's works are spaced several months apart.

On Monday, a depiction of a goat precariously perched on top of a wall with rocks tumbling down appeared in Richmond, southwest London.

"I think it's actually a mountain gazelle from Palestine. So I think that work has to do with Palestine," Daniel Lloyd-Morgan, a 60-year-old artist told AFP.

Then on Tuesday two elephant silhouettes with their trunks stretched towards each other appeared in Chelsea, southwest London.

On Wednesday, the black silhouette of three monkeys appeared on the side of a railway bridge as if they were swinging.

"Banksy is trying to get us to think and reflect about the ecological crisis that really threatens humanity," university professor Fawaz Gerges told AFP as he admired the latest work.

"His focus seems to be on animals, on trees, on oceans and it's an overarching theme of his in the past few months," he added.

The artworks have appeared at a time when England is gripped by violent far-right, anti-immigrant protests over the murder of three girls. Demonstrators have targeted hotels housing asylum seekers.

Banksy, whose identity is unknown, has repeatedly shown sympathy for the plight of refugees.

At the Glastonbury music festival last month the artist launched an inflatable boat over crowds depicting dummy migrants wearing life vests.