GALLIPOLI - The catastrophe of Gallipoli 90 years ago scarred New Zealanders' hearts and caused immense grief to families, Prime Minister Helen Clark told an Anzac Day service today at the site where so many died.

At the Chunuk Bair memorial overlooking the Narrows in the Dardanelles, Miss Clark told thousands of New Zealanders and Australians, the human sacrifice was felt throughout the land and few communities were left untouched.

What began as a great adventure became a nightmare which was to be repeated on the Western Front in France and Belgium in the next three years.

"Yet it also stirred within our people a new sense of national identity.

"It is said the troops left home as colonial soldiers in the service of the empire but returned as New Zealanders," she said.

"We look back with awe at the incredible courage the New Zealanders displayed at Gallipoli and in the following campaigns in the Great War.

"Facing incredible odds, and often poorly clothed, fed and armed, they nonetheless fought with courage and with honour -- attributes which we value greatly to this day."

Miss Clark said at Gallipoli more than two thirds of the New Zealand dead were never identified and had no known grave.

She said that was why the Tomb of the Unknown Warrior was established -- to give a focus for remembrance of all those who died serving New Zealand overseas.

Miss Clark said tribute must also be paid to the brave Turkish soldiers who gave all for the defence of their homeland.

"They won the battle here and the whole campaign but at a terrible price."

She said that could have been the basis for long term bitterness but instead, under the leadership of Ataturk, Turkey offered reconciliation to its former adversaries with his famous words to the families of the fallen.

They were: "You the mothers who sent their sons from far away countries, wipe away your tears; you sons are now lying in our bosom and are at peace. After having lost their lives on this land, they have become our sons as well."

"Those truly were the words of a great man," Miss Clark said.

She said to understand what happened at Gallipoli was to understand what shaped the young nation of New Zealand.

Of the population of one million about 10 percent served overseas in World War 1.

She said 21 years later New Zealanders served in World War 2 and in the 1950s, the 1960s, and the 1970s more New Zealanders were deployed to conflicts off shore.

She said New Zealanders were drawn to Anzac Day services by a "simple sense of solidarity with those brave New Zealanders who served their country and never came home.

"Anzac Day is never a day for celebration. It is a day for reflection and remembrance," she said.