The authorities in Seoul say the dogs had been infected, or vaccinated, with disease-causing agents, which could make humans ill if the dogs were eaten.

Dog soup, or poshingtang, is an expensive dish popular in summer with older Korean men and renowned for its health-giving properties.

However, the BBC correspondent in Seoul, Andrew Wood, says many younger Koreans are disgusted and embarrassed by the practice of eating dogs.

The prosecutors say poshingtang restaurants in the Seoul area have been supplied with nearly 6,000 dogs over five years. Each animal was worth around $80.

Bodies should have been burnt

They said most of the dogs had suffered from pneumonia or gastro-enteritis but 860 had been vaccinated against rabies.

Their bodies should have been incinerated but apparently fell into the hands of unscrupulous dog meat traders.

Two men have been arrested. One ran a dog-breeding farm, the other was the head of a government research laboratory.

Prosecutors say the two men were not connected. They are widening their investigations to include wholesale butchers and other research centres.