More than two weeks after the food poisoning outbreak was first reported in the north of the country, the number of confirmed or suspected cases has reached 1,200, according to media reports.

There was no immediate official confirmation of the figure, but the Stockholm-based European Centre for Disease Prevention and Control has described the outbreak of potentially deadly strain of E coli as "one of the largest worldwide and the largest ever reported in Germany".

Authorities warned against eating raw vegetables after traces of the bacteria were found on organic cucumbers from Spain last week. But confusion reigned on the source of the outbreak.

Enterohaemorrhagic E coli (EHEC) can result in full-blown haemolytic uraemic syndrome (HUS), a disease that causes bloody diarrhoea and serious liver damage and which can result in death.

"Normally we see about 1,000 cases per year, but we've now had some 1,200 cases in just 10 days," Jan Galle, director of the Luedenscheid clinic in western Germany, told ZDF public television.

"And we know that this time the EHEC strain is especially virulent and resistant, and has led to a very high number of HUS" cases, he added.

The Robert Koch Institute (RKI), Germany's national disease institute, warned people not to eat raw cucumbers, tomatoes and lettuce, especially in northern Germany where the outbreak began.

It reported 329 confirmed HUS cases nationwide and three confirmed deaths.