Image copyright EPA Image caption The new commission is Gift Horse by German artist Hans Haacke

Gift Horse, a skeletal sculpture which displays a live feed from the London Stock Exchange, has been unveiled in Trafalgar Square.

The equine bronze, by German artist Hans Haacke, is the tenth artwork to occupy the Square's Fourth Plinth.

London mayor Boris Johnson described the work as "a startlingly original comment on the relationship between art and commerce".

It replaces a giant blue cockerel which was on display for 18 months.

The riderless horse - with an electronic ticker of share prices, displayed on a bow around one of its front legs - is a wry reference to an equestrian statue of William IV originally planned for the plinth, but which never came to fruition due to a lack of funds.

Image copyright EPA Image caption The horse's front leg has an electronic ribbon displaying live the ticker of the London Stock Exchange

Haacke, 78, who is based in New York, was inspired by an engraving in The Anatomy of the Horse (1766) by English painter George Stubbs, whose works are on display in the National Gallery, on Trafalgar Square.

At Thursday's unveiling, Haacke was reluctant to explain what his sculpture was trying to say.

"It is an invitation to make connections," he told the BBC, "but I would not like to give directions. I'm sure there will be a diversity of responses. That is not only true for this but any kind of art."

Image copyright EPA Image caption The sculpture was unveiled by London Mayor Boris Johnson

Boris Johnson said: "There will be those that say this undeniably unfed, emaciated quadruped is a warning, a memento mori, a symbol of the pursuit of austerity and the [Chancellor of the Exchequer] George Osborne diet approach to life.

"But I say no, my friends. This wonderful sculpture stands for the horse in all its incarnations... in these fabulous tubular structures we see symbolised the vital infrastructure - the tube - that must run beneath the surface of any great and beautiful city."

Gift Horse drew positive, if slightly bemused, comments from tourists.

One of the first people to see it was Tim Wright from Lancashire, who told the BBC: "I find it pleasing to look at but I've not a clue what it's trying to say."

Image copyright EPA Image caption Artist Hans Haacke likes to examine the relationships between art, power and money

Image copyright EPA Image caption Haacke's Gift Horse is the 10th sculpture to appear on the Fourth Plinth

"It's wonderful to see something unusual," said Georgia Bartlett, on a day trip from Poole in Dorset. "What's it saying? I just don't know. But it's a beautiful sculpture against the skyline."

Booker Prize-winning author Howard Jacobson, who was walking through Trafalgar Square as it was unveiled, said: "I'm very pleased the blue cockerel is gone - I enjoyed that joke for a weekend.

"I really like this. This is what the Stock Exchange has done to the body of the horse. It's a good conceit - I'm for it. But I might have changed my mind by the end of the weekend."

Mark Wallinger's figure Ecce Homo was the first piece to stand on the empty plinth - in the northwest corner of the square - in 1999.

Other works include Alison Lapper Pregnant by Marc Quinn (2005), Nelson's Ship in a Bottle by Yinka Shonibare (2010) and Elmgreen and Dragset's Powerless Structures, Fig 101 - a sculpture of a boy astride his rocking horse.

The next sculpture on the plinth - to be unveiled in 2016 - is British artist David Shrigley's bronze artwork Really Good. It consists of a hand with a disproportionately long thumb.