As German doctors are looking for the source of the deadly bacterial intestinal disease, Russia has decided to ban the import of all fresh vegetables from Europe.

The temporary ban imposed Thursday enhances the previous regulation, which only covered cucumbers imported from Spain and Germany. Cucumbers were believed to be behind the pathogenic strain of E. Coli, but the assumption was later proved wrong.

The ban will be in force for as long as is necessary to protect Russian residents from the poisoning risk, Russia's sanitary regulator said. The initial import restriction was imposed on Monday.

The European Commission deems the ban of all vegetables "disproportionate" and is to send an official request to clarify the situation to the Russian watchdog in a matter of days, said a spokesman for the EU Commissioner for public health, John Dalli.

"I believe that the situation with the E. Coli is short-term. It's a well-known microbe and we know well how to deal with it. It's not like the avian flu or the mad-cow disease... I hope the authorities will respond with a swift lifting of the vegetables ban, when the time comes, just as they did with imposing it. I believe it will happen in several days," Rostislav Ordovsky-Tanaevsky Blanco, owner of the fast food chain Rostik International told RT.

Meanwhile Spanish farmers threaten to sue German regional authorities for damages after they blamed their cucumbers for the outbreak. They say the accusations have led to sales losses of 200 million euros in the last week.

Germany is still trying to find the source of the outbreak, which is continuing to infect people in the country, with nearly more than 1,200 suspected cases registered in Germany, Austria, the Czech Republic and Switzerland. The outbreak has caused up to 17 deaths, preliminary reports say.

The World Health Organization reported on Thursday that the E. coli strain responsible for the deadly outbreak has never been seen before. Preliminary genetic sequencing suggests the strain is a mutant form of two different E. coli bacteria, the agency said.

Hamburg health senator Cornelia Prufer-Storcks said in an interview on Thursday that the disease may be transmittable from human to human, reports RIA Novosti. The official cited data from the Robert Koch institute, one of Germany's leading institutions for infection research.

Russia's Chief Medical Officer Gennady Onishchenko believes the EU health watchdog has failed to provide sanitary security.

"I'm not implying that my colleagues in Germany and other European countries lack professionalism. But they are bound by a legal basis for investigating infection outbreaks and establishing the culprits, which is overpoliticized and detached from reality," he said.