SKARYSZEW, Poland: Polish animal rights campaigners heckled traders at one of Europe's biggest horse-trading fairs on Monday to try to prevent them selling the animals for meat.

Horse breeders have been coming to the open-air fair at Skaryszew the same day every year for the past three centuries, but the tradition is under pressure from activists and, this year, from concern about the Europe-wide trade in horse meat.

Starting in the early hours of Monday morning, small groups of activists approached breeders at the fair, in a town about 120 km (75 miles) south of the Polish capital, and tried to prevent them selling their horses.

In one confrontation, an activist shouted at a breeder: "You won't sell that horse. That horse is ill."

Some of the breeders got into angry confrontations with the activists, though there were no physical clashes.

One trader swore at the activists and told them to go away. "This is none of your business," he said.

The night-time fair in Skaryszew, the biggest in Poland, has taken place every year on the first Monday after the religious holiday of Ash Wednesday since the 17th Century.

Thousands of horses and their handlers mill around in fields off the town's Mickiewicza Street. Some of the horses are sold to slaughter-houses for their meat. The breeders say this is only a small proportion of the sales but activists say that is what happens to most of the horses sold at the fair.

The practice has come under renewed scrutiny after British and Irish inspectors found some supermarkets were selling horsemeat labelled as beef.

The Irish government said some of the suspect meat came from Poland, but Polish food safety agencies say their checks had turned up no evidence of this.

Scarlett Szylogalis, head of the Tara Foundation Horse Shelter, an animal rights group which organised some of the protests, said that she wanted the Skaryszew fair closed down.

"A horse should be a companion, not an animal for slaughter," she said. "We are fighting for a change in the law. We have to change it."

One horse breeder, from south-eastern Poland, who gave his name as Andrzej, said he had not yet made any sales but would stay until he had sold all his horses.

"Protests? Yes, of course I saw some," he said. "These young people protest against selling horses for meat. But if they don't allow us to sell horses for meat, those animals will be transported abroad and killed there."