OTTAWA -- When they left on vacation Jim and Marnie Livezay of Nocona, Tex., a small cowtown on the old Chisholm Trail, never expected to be standing in the middle of a crowd of more than 100,000 Canadians on Parliament Hill yesterday, singing the Star-Spangled Banner and wiping tears from their eyes.

The retired couple had travelled as far as the border crossing at Sault Ste. Marie when they heard the first frightening news reports from New York and Washington on the car radio Tuesday morning.

They briefly thought of turning around, but figured Canada was one place where they could feel safe. They were on the outskirts of Ottawa yesterday morning when the radio told them about the noonhour memorial service on Parliament Hill for the victims of the terrorist attacks.

Thus they found themselves on foreign soil, in the shadow of the Peace Tower, listening to a Canadian Forces band play O Canada,and then their own national anthem.

They wept. And they sang loudly despite the lumps in their throats.

"I don't think I've ever seen a crowd like this before. God bless the Canadians," Mr. Livezay said, looking out at a throng that included Governor-General Adrienne Clarkson, Prime Minister Jean Chrétien, most of the Liberal cabinet, the leaders of other political parties, and thousands of ordinary Canadians who came to show solidarity with the United States during one of its darkest moments.

"We really feel you Canadians are our best friends," Mrs. Livezay added. "This is unbelievable."

Ms. Clarkson called for everyone to rise for a silent tribute. For three full minutes the only sound on Parliament Hill was the flapping of Canadian and American flags, draped in black crepe and flying at half-mast.

Hundreds of thousands more gathered where they could across the country yesterday to observe the silence, from provincial Parliaments to shopping malls, city halls and office complexes.

Hundreds at a service in Calgary stood and applauded as three firefighters, perched high above on a crane, saluted the crowd, an American flag draped in front of them.

North Carolina residents John and Trish McCain wept as an RCMP officer in red serge sang their national anthem at a brief memorial service at Halifax International Airport yesterday.

"The show of unity has been incredible. The compassion of Canadians has been incredible," Ms. McCain said. "We're really touched what the Canadian people have done for us."

In Ottawa, U.S. Ambassador Paul Cellucci made the same point, thanking Canadians for embracing and caring for more than 25,000 Americans whose flights were diverted to Canadian airports in the chaotic hours after the hijack attacks.

Mr. Cellucci said the flowers and notes of condolence that had been left at the embassy gates touched him. "You truly are our closest friends."

He said Americans will need Canadian help and support in the days and months ahead.

Canada and the United States are free and open democracies, he said. "And our way of life will be maintained."

The crowd applauded when Mr. Cellucci said Canada, the U.S. and other democracies "will win this war against terrorism."

Mr. Chrétien said the tragic events of this week, in which scores of Canadians are believed to have died with thousands of Americans, make the countries like one family. "At a time like this, it is our feelings, our prayers and our actions that count."

He told Mr. Cellucci that Canada and the U.S., together with other allies, "will defy and defeat the threat that terrorism poses."

The invited dignitaries included clerics from Christian, Jewish, Islamic, Hindu and other faiths, ambassadors from foreign countries and the Palestinian representative, Baker Abdel Munem, who signed the book of condolences in English and Arabic.

Pride of place in the official honour guard went to Mounties and Ottawa firefighters, who came to pay tribute to their heroic brothers and sisters in New York city.

Ms. Clarkson prayed that the "spirit of peace and the love of human beings for each other be shown in our sympathy to all Canadians, Americans and others whose lives have been horribly changed by this terrible tragedy."

At Queen's Park in Toronto, Ontario Lieutenant-Governor Hilary Weston told a memorial service that "if the perpetrators of these foul acts thought to frighten the Americans, our friends and neighbours, they were sadly mistaken." Across town at BCE Place, Louise Lanctot waited for the start of a brief memorial for those caught in this week's tragedy -- including some missing friends in New York.