STOCKHOLM (Reuters) - Swedes wept and laid red roses to mourn murdered foreign minister Anna Lindh on Thursday amid a wave of national grief and incredulity as tributes poured in from world leaders.

"Sweden has lost its face toward the world," Swedish Prime Minister Goran Persson said.

In Geneva, U.N. Secretary-General Kofi Annan called Lindh a "great foreign minister, a great Swede and a great European."

Lindh, a 46-year-old mother of two, was stabbed by an unidentified attacker in a Stockholm department store on Wednesday.

The Swedish flag flew at half mast at the entrance of the Karolinska hospital where she died from her wounds at 5:29 a.m.

Visitors wept and placed roses, the symbol of Lindh's Social Democrat Party, by the flagpole. A tribute from youth groups of political parties read: "We think about you, Anna Lindh."

Lindh's stabbing evoked dark memories of the killing of Prime Minister Olof Palme in a city center street in 1986. For many, that assassination dispelled an illusion that the country was immune from political violence.

"The grief, anger and despair the murder of Anna Lindh evokes is indescribable," said Christian Democrats leader Alf Svensson. "What should not happen has happened once again."

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Other Nordic political leaders signaled that a rethink on security could be on the agenda.

"This is a wake-up call for us in Norway," Norwegian Prime Minister Kjell Magne Bondevik said. "We want contact between politicians and other people and we may now have to consider if we should do it differently."

World leaders also paid tribute to Lindh, who had been a leading campaigner for her country to vote "Yes" to joining the European Union's single currency in a referendum on Sunday.

"It is with great sadness that I heard the tragic news... her murder is a terrible blow to all who knew her," Secretary of State Colin Powell said in a statement.

French President Jacques Chirac called the Swedish prime minister to express his "great sadness and consternation."

"The beauty that she had in her face was a representation of the beauty she had in her soul," EU foreign policy chief Javier Solana said at a news conference in Brussels.

British Foreign Secretary Jack Straw said she was "someone full of life who represented something wonderful in Sweden and Europe."

Tributes came from other foreign ministers including France's Dominique de Villepin, Germany's Joschka Fischer and Russia's Igor Ivanov.

Romano Prodi, President of the European Commission, said he was filled with dismay at news of the "blind attack" on Lindh.

"The world on the 11th of September, with horrible irony, has lost another very substantial contributor to a better and safer world," NATO Secretary-General George Robertson said.

EU ambassadors held a minute's silence during a session in Brussels, while in the southern Swedish town of Barseback it was announced that competitors would wear black armbands at the golf Solheim Cup -- the world's top team competition for women.

Sweden's national soccer coach canceled a news conference after Sweden beat Poland 2-0 to win a place in Euro 2004.