GENEVA - THE world must be ready for H1N1 swine flu to become more severe and kill more people, World Health Organization chief Dr Margaret Chan said on Friday.

A genetic analysis of the new virus showed it must have been circulating undetected for some time, in pigs or perhaps in other animals.

ATHENS - MUSLIM immigrants clashed again with Greek police on Friday during a second day of protests in Athens over charges that officers tore up a Koran during an identity check of immigrants.

Nearly 1,000 Muslims rallied in the city's central Omonia square in a demonstration organised by leftist, immigrant and anti-racism groups.

WASHINGTON - THE most complete analysis yet of the new H1N1 flu virus shows it must have been circulating undetected for years, most likely in pigs, researchers said on Friday.

They said it is important to start doing better surveillance of influenza viruses in pigs, as they are clearly a potential source of human pandemics.