It was the first major battle of World War I for Australian and New Zealand troops, who were sitting ducks landing in a hail of bullets as they attempted to take the Ottoman Empire out of the war.

The sheer magnitude of the "butcher's bill" was unprecedented, Governor-General of New Zealand Dame Patsy Reddy told the service.

"Such were the losses that during the course of the campaign the New Zealand units engaged here had to be reinforced by more than 100 per cent of their original strength," she said.

"Australian units experienced a similar attrition."

A quote from former President of the Republic of Turkey, Mustafa Kemal Ataturk, was read aloud by a Turkish Army colonel to highlight that those who died 103 years ago are now "in the soil of a friendly country" at peace.

From this unfathomable loss, Australia's national identity was forged, Home Affairs Minister Peter Dutton said.

"It is humbling to stand among our New Zealand and Turkish friends and reflect on the service and sacrifice of the tens of thousands of people on both sides of the campaign who lost their lives," he said.

"A legacy of resilience, determination, facing decisions and sights we would never wish upon anyone.

"They are at the core of our people and our purpose. And for this, we will be eternally grateful. Lest we forget."

The voices of The Choir of St James' from Sydney rang out over Anzac Cove as dawn broke.

Earlier, New Zealand's army chief Major General Peter Kelly painted a picture of the horrors Aussie and Kiwi troops faced on April 25, 1915, with machine guns pointed at them from cliffs still shrouded in darkness.

He noted the youth and inexperience of those forced to make "hideously difficult" decisions under pressure.

"And as night gave way to day, they wondered if they would be found deficient in courage," Maj Gen Kelly said.

"For hundreds it would be their last day on earth.

"The passing of time has not diminished the tragedy of what occurred here."

Six students from East Loddon College in central Victoria were among those who lined the coastline, standing for the first time at the service alongside pupils from their Turkish sister school.

"I think it shows peace is possible and schools on opposite sides of the world can come together and share in a significant day ... and have the same values and beliefs," principal Steven Leed told the Seven Network.

But the pilgrimage was not smooth-sailing for everyone in the crowd after a bus carrying 45 people, mostly young Australian and New Zealand travellers, burst into flames en route to the service from Izmir in Turkey.

All personal belongings were destroyed in the charred wreckage, however it is understood no one was injured.

Australian Associated Press