Trade unions around the world have launched a boycott of Coca-Cola products, alleging that the company's locally owned bottlers in Colombia used illegal paramilitary groups to intimidate, threaten and kill its workers.

The unions claim Coca-Cola bottlers hired far-right militias of the United Self Defence Forces of Colombia (AUC) to murder nine union members at Colombian bottling plants in the past 13 years.

Two years ago, the Colombian food and drink union Sinaltrainal sued Coca-Cola and its Colombian bottling partners in a US federal court in Miami over the deaths of its members.

The suit alleged that the bottling companies "contracted with or otherwise directed paramilitary security forces that utilised extreme violence and murdered, tortured, unlawfully detained or otherwise silenced trade union leaders", and that Coca-Cola was indirectly responsible for this.

In March, the judge removed Coca-Cola from the suit, but the process against the bottlers continues. The unions have appealed against the court's decision.

While the case continues, unions are calling on consumers to stop drinking Coke and other Coca-Cola products. The campaign was launched simultaneously in countries including the UK, US, Germany, Italy and Australia.

Javier Correa, the president of Sinaltrainal, said the campaign aimed to put pressure on Coca-Cola "to mitigate the pain and suffering" that union members had suffered.

Coca-Cola said in a statement on Tuesday that the allegations against the company and its partners were "completely false", and that the campaign was "nothing more than a shameless effort to generate publicity".

But Mr Correa insisted that - despite increased international attention - actions against union members have continued.

He said that in May, an anonymous caller to the union headquarters in Colombia warned that the offices would be targeted for a bomb attack. In March, a worker in the city of Bucaramanga received a notice from paramilitary groups that he had been declared a military target.

While the plight of Colombia's Coca-Cola workers has become well-known overseas, local media were making no mention of the campaign yesterday.

"In Colombia it is very difficult for this type of case to make it into local media," Mr Correa said. "It's all part of the culture of impunity."

Sinaltrainal decided to seek international support after it became frustrated with the courts' delays in considering the deaths of its workers.

"Cases that are 13 years old still have not been cleared up - no one has been detained and the cases end up unresolved," said Mr Correa.

One of the union's accusations is that managers at a bottling plant in the town of Carepa in northern Colombia directed paramilitary fighters to kill two union leaders in 1994. Two years later a member of the union's executive board was killed at the plant by paramilitary gunmen, the lawsuit says.

The latest death of a Sinaltrainal member happened last August, when Adolfo Munera was murdered in Caribbean coastal city of Barranquilla. A week earlier, the country's highest court had ordered the city's Coca-Cola bottler to re-employ him, after he was cleared of criminal charges filed against him in 1997

Coca Cola's Colombian bottlers have also denied the accusations. Colombia is the world's most dangerous country in which to be a union member, with 184 of the world's 213 confirmed killings last year, according to the International Confederation of Free Trade Unions.