Spain has complained formally to Germany and the European Union over Berlin's handling of a virulent super-bacterium which has killed six people and infected around 800 others, dpa reported. Cases have also been reported in Britain, the Netherlands, Sweden, Denmark and most recently Austria, where two German tourists were said on Friday to have fallen ill. Germany this week claimed to have sourced the infection to Spanish cucumbers, but informed press about the a sub-strain of E. coli known as enterohaemorrhagic Escherichia coli (EHEC) - before informing the EU, as it should have done, according to Josep Puxeu, Spain's minister of state for rural affairs. Spain has stopped cucumber deliveries that the disease has been linked with, but argues there is no proof that EHEC entered Germany through its products. The origin of the bacterium remains unclear, Spanish Health Minister Leire Pajin and Agriculture Minister Rosa Aguilar stressed. The World Health Organisation is sharing information with health authorities in other countries and has offered technical assistance, but did not recommend travel or trade restrictions for Germany. "Most of the cases reported outside Germany concern either German nationals visiting the other affected member states or persons who had been visiting Germany," the European Commission noted in a statement. Aguilar said the cucumbers under suspicion belonged to a variety that is not usual in Spain, whilst Pajin said she asked the European Food Safety Authority to join the investigation on the origin of the bacterium. Nobody has been infected by it in Spain so far, she added. Officials both in Germany and Denmark have reported finding the bacterium on Spanish cucumbers, although experts have stressed that this was not necessarily the sole source of the outbreak. A spokesman for EU Health Commissioner John Dalli noted on Friday that such a contamination "could occur at any stage." EHEC infects an average of 800 to 1,200 people every year. Researchers say it has never before caused an outbreak of this scale. The current cases are also unusual because they feature potentially fatal symptoms in adults, mostly young women. The bacterium usually affects children. Symptoms of those gravely ill include internal bleeding, diarrhoea and kidney failure. German authorities have warned against eating lettuce, cucumbers and raw tomatoes, not ruling out that EHEC may be present in other vegetables.