The accident happened during a performance by the American rock group, Pearl Jam, at the Roskilde annual festival near Copenhagen.

There were scenes of pushing, panic, shouts, then the music stopped, replaced by howls and screams. It was unbearable.

Eyewitness

Police said that the grounds were muddy after day-long rain, and the victims, who were pressed up against barriers in front of the stage, slipped and fell.

They were trampled to death as the crowds behind them surged forward.

"A group of some 15 spectators collapsed en masse in front of the rostrum, and people behind them began uncontrollably tumbling over them," one eyewitness said.

The band expressed anguish over the deaths

Another eyewitness said: "The people massed at the back kept on pressing towards the front of the stage despite appeals by the security guards and the singers."

"All of a sudden there were scenes of pushing, panic, shouts, then the music stopped, replaced by howls and screams. It was unbearable."

Witnesses said that the band had repeatedly urged fans to pull back from the stage before the accident occurred.

A police spokesman said that altogether 26 people had undergone hospital treatment, and three had been seriously injured.

In a statement, Pearl Jam said: "There are absolutely no words to express our anguish" over the deaths, which it called a "horrible nightmare".

Grim atmosphere

News of the disaster, which occurred shortly before Friday midnight, was announced by the festival director, Leif Skov, who got up on the stage and asked for a minute's silence.

Our lives will never be the same, but we know that is nothing compared to the grief of the families and friends of those involved

Pearl Jam

He said that performances on the festival's main stage would be halted until Saturday, but other concerts continued overnight.

Reports from Roskilde early on Saturday say that the atmosphere there was grim.

A 20-year-old woman there named only as Inger said that she wanted to go home now: "The fun has been ruined. My heart's not in it any more," she said.

She said she no longer wanted to see her idols close up for fear that she too might be crushed to death.

It was Roskilde's first major incident in 30 years

The victims are not being publicly identified until their families have been informed, but one report quoted police as saying they were all male and at least one was foreign.

The BBC's Michael Voss in Copenhagen says there is a great sense of shock and sadness in Denmark at the news, which has dampened what was meant to be a day of celebration over the opening of a bridge and tunnel link with Sweden.

Woodstock model

The festival has two more days to run, but the police and organisers are due to decide on Saturday whether or not it should continue.

The Roskilde festival, held every year since 1971 on a farm near Copenhagen, was inspired by the 1969 Woodstock Festival in the United States.

Last year, it drew some some 100,000 people - making it one of the biggest rock events in Europe, with crowds coming particularly from the Nordic countries and Germany.

A total of 175 bands are performing this year on seven stages, with star attractions including The Cure, Oasis, Lou Reed, the Pet Shop Boys, Willie Nelson and Family, and Iron Maiden.