BERLIN - An E. coli outbreak linked to contaminated cucumbers that has killed 14 people and made more than 300 seriously ill in Germany has spread to other north European countries and is expected to worsen in the coming week.

"We hope that the number of cases will go down but we fear that it will worsen," said Oliver Grieve, spokesman for the University Medical Centre Schleswig-Holstein in north Germany, where many of those afflicted are being treated.

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The source of the virulent strain of the bacteria is unknown, German authorities said on Monday ahead of a crisis meeting of federal and state officials in Berlin. Most of the deaths have been in northern Germany.

The E. coli pathogen has been identified on cucumbers imported from Spain but it is unclear if they were contaminated there, during transport or in Germany.

There are 36 cases of suspected E. coli in Sweden, all linked to travel in northern Germany, authorities said. A small number of cases have been reported in Britain, Denmark, France and the Netherlands, all linked with travel to Germany.

The German government has identified the pathogen as hemolytic-uremic syndrome (HUS), a serious complication of a type of E. coli known as Shiga toxin-producing E. coli (STEC), and said it had killed 14 people and made at least 329 ill.

The European Centre for Disease Prevention and Control (ECDC) said in a risk assessment that the HUS/STEC outbreak is one the largest in the world of its kind.

HUS affects the blood, kidneys and, in severe cases, the nervous system and can be particularly serious for children and the elderly. Some 60 cases of HUS are reported annually in Germany, the government said.

Grieve said his hospital had 82 cases of HUS and 115 confirmed E. coli cases, and said the number of cases there had doubled within the past few days.

The northern port city of Hamburg alone has reported 488 cases of E. coli since the outbreak began in mid-May and has 94 cases of HUS.

A hospital in the city said it was transferring patients with less serious illnesses to other clinics to cope with the flood of HUS patients.

Spain meanwhile said on Monday it was mulling taking action over Spanish cucumbers being blamed for the outbreak.

"There is no proof of this and so we will demand explanations from who has attributed this matter to Spain," Diego Lopez Garrido, secretary of state for the European Union, told journalists.

Horticultural farms in the southern Spanish region of Andalusia have been losing 7-8 million euros a day since German authorities linked the bacteria to Spanish cucumbers last week.

German authorities have warned consumers to avoid eating cucumbers, lettuces and tomatoes and have ordered some products removed from store shelves.

"As long as the experts in Germany and Spain have not been able to name the source of the agent without any doubt, the general warning for vegetables still holds," German Consumer Protection Minister Ilse Aigner said on Sunday.

Authorities in Sweden have warned Swedes travelling to north Germany to steer clear of cucumbers, tomatoes and salad.

Austria's food safety agency ordered a recall of organically grown cucumbers, tomatoes and eggplant supplied by a Spanish producer thought to be the source of the outbreak. It said 33 Austrian stores were affected.