Lindh, 46, who had been tipped as a future prime minister and was a leading campaigner for Sweden to join the European Union's single currency in Sunday's referendum -- now in doubt -- was stabbed repeatedly in a Stockholm department store.

"Her family has lost a mother and a wife. Social Democracy has lost one of its most gifted politicians. The government has lost a skilled politician and a good colleague. Sweden has lost its face toward the world," said Prime Minister Goran Persson.

Tributes to one of Sweden's most popular politicians had poured in from all over Europe as surgeons at Stockholm's Karolinska hospital struggled all night to save her life.

But Thursday the hospital issued a statement saying that Lindh had died of "massive bleeding caused by knife wounds to the liver and many of the big blood vessels in the abdomen."

The stabbing took place in the final days of campaigning for the referendum, but it was not clear whether they were linked.

Politicians were to meet at noon to decide whether the referendum should go ahead. Lindh had campaigned for the pro-euro side, which has trailed opponents in opinion polls.