Police in Cairo clashed on Sunday with angry pig farmers who hurled stones and bottles to try to stop their animals from being forcibly taken away to be slaughtered as a precautionary measure against the virus that causes swine flu in humans.

Egypt has not recorded a single case of the H1N1 virus and its pig herds are free from swine flu, but the government last week decreed a cull of all the estimated 300,000 pigs in the country.