Israel mourned the six million Jews who perished in the Holocaust with nationwide ceremonies on Thursday, 60 years after Soviet troops liberated the Nazi death camps.

Israeli Prime Minister Ariel Sharon arrived in Poland on Thursday, accompanied by 20 Holocaust survivors, to join a commemoration ceremony at the Auschwitz-Birkenau complex, the largest camp built by the German Nazis in Poland.

About 20,000 people, including the prime ministers of Poland and Hungary, took part in the annual ceremony known as the March of the Living to mark Holocaust Remembrance Day.

"I am naturally very moved to be on the spot where the worst happened," Sharon told journalists.

The three-kilometre procession began at the Auschwitz gate that has the inscription "Arbeit Macht Frei" (Work sets you free) and ended at the Birkenau camp, in honour of the six million victims of the Holocaust, known as the Shoah in Hebrew.

"We have learnt the lesson of the Shoah. The Jews will never again be left without a home or a Jewish defence force to protect their lives," Sharon said Wednesday in Jerusalem.

"We are alone with the victims of the darkest chapter in human history and the most tragic chapter in the history of the Jewish people. A horrific night which lasted six long years and during which six million Jews were executed."

The solemnity of the day was marred by the discovery of swastika graffiti on walls near the Yad Vashem Holocaust memorial in Jerusalem.

Elsewhere in the city, slogans in Hebrew scrawled on buildings compared Sharon to the Nazi dictator Adolf Hitler. There are reports that police have launched an investigation.

Officials suspect the graffiti was the handiwork of far-right extremists angry with Sharon over his plan to pull Jewish settlers out of the Gaza Strip.

He plans to evacuate all 21 Jewish settlements in the Gaza Strip and four of 120 in the West Bank.

Israeli cabinet minister Isaac Herzog, who is expected to be attending the Poland ceremony with Sharon, said "only a sick mind could compare the prime minister to the Nazi enemy on Holocaust Remembrance Day".

"Unfortunately, there are no limits to the ignorance, evil and inhumanity of those on the fringes of the extreme right," Herzog was quoted as saying on the website of Israel's Haaretz newspaper.

Canada remembers

Meanwhile, Canadians marked Holocaust Remembrance Day in ceremonies in Ottawa and Toronto.

"This must never happen again," said Prime Minister Paul Martin at a commemoration on Parliament Hill.

Conservative leader Stephen Harper said the world must ensure that genocide is never be allowed to happen again. In Africa, Asia or in the heart of Europe.

In Toronto, at the largest remembrance ceremony outside of Israel, Holocaust survivor Arnold Friedman read a poem describing the "gaping, fiery furnaces" that fed on humans, "day and night."

Friedman lived through nine horrifying months in Auschwitz.

"You not only saw the crematoria. You not only saw the train loads of people going in there," he said. "You also saw the stench. You smelled the smoke."

Friedman's entire family -- his mother, father, two brothers and two sisters, all perished in Auschwitz. He said it's only in remembering the horrors of the Holocaust that we stand any chance of avoiding its repetition.

Harold Davis, National President of B'nai Brith Canada, said the Holocaust teaches that none amongst us is immune to hate and its dangerous consequences.

"We hope that this ceremony will be a springboard for establishing this day as an integral part of Canadian tradition and consciousness," he said in a statement.