It is believed the men in their late 20s jumped onto a bed which was part of an exhibition by young British artist Tracey Emin, and threw bits of the artwork around.

The BBC's John Kay: "There were claims yesterday that performance artists would carry out an attack of this sort - or worse"

They were arrested for criminal damage and are being held in custody at Belgravia police station.

The Tate later released a statement confirming that an incident had taken place at around 1pm.

A spokeswoman said: "The work has now been restored and the exhibition will open to the public as usual at 10am on Sunday."

Emin's work has caused the most controversy among the work of the five artists shortlisted for the £20,000 Turner Prize and on display at a special exhibition hall at the Tate.

In a spin: Steven Pippin's laundry photos

Emin has supplemented her usual self-confessional videos, embroideries and sketches with a display of her own bed complete with real personal detritus.

Empty vodka bottles, used condoms, soiled underwear, and a stained mattress, pillows and duvet arguably sum up a career in which Emin has made public her appetites for sex, alcohol and frankness.

The bed has caused strong, if mixed, reactions in the four days for which it has been on display.

The response has ranged from effusive praise to outrage and questions along the lines of "Is this art?"

But curator Jay Jopling is a fan, and Charles Saatchi, the most famous patron of young British artists, paid a reputed £40,000 for a previous Emin work, a name-embroidered tent entitled Everyone I Have Ever Slept With 1963-1994.

Steve McQueen: Artistic stunt or stunt artist?

The other Turner candidates - Steve McQueen, Steven Pippin and Jane and Louise Wilson - are not popular with traditionalists either.

Pippin turns objects such as washing machines into cameras in a strange homage to the pioneers of photography, displaying his quirky gadgets alongside the photos.

The Wilsons show videos of empty Las Vegas casinos and the cavernous Hoover Dam.

Steve McQueen's Deadpan - a video which sees the artist pass through the window of a falling wall à la Buster Keaton - incites the viewer to imagine how the stunt is achieved.

Stunt is perhaps a fitting word for the Turner Prize, with some critics suspicious that the jury pick not the best work by young British artists, but the most shocking.

However, the exhibition is also extremely popular with the public.

Turner winner Ofili was at the centre of a row earlier this month

More than 120,000 people visited last year's Turner exhibition, and countless column inches have already been devoted to this year's. It will even have its own show on Channel 4.

The Turner Prize was won last year by Chris Ofili, who incorporates elephant dung into his psychedelic paintings which draw on contemporary black popular culture.

The previous year it was won by Damien Hirst's pickled shark.

Ironically, both these artists were at the centre of controversy themselves earlier this month, when the British Sensation exhibition went on show in New York.

The show included Ofili's depiction of a black Virgin Mary made with elephant dung and pictures cut from pornography magazines, and pickled cow parts from Hirst.

The city pulled its funding, protesters took to the streets and an age-old debate over free speech was back on the agenda.

Hindley: Portrait was vandalised at the Royal Academy

Yet with 9,000 New Yorkers visiting the exhibition on its opening day, the show gave the Brooklyn Museum of Art its largest opening in the museum's 175-year history.

The same exhibition attracted controversy when it showed at the Royal Academy in London.

Marcus Harvey's portrait of child-killer Myra Hindley, made out of children's handprints, was vandalised.

However, the exhibition became one of the Academy's most successful of all time, visited by 284,734 people over three months.