"It's fast becoming a rite of passage in terms of making sure that you get to the dawn service. And for a first-timer, it's quite extraordinary. They can't get over how many people turn up."
Dr Clarke said there was a real opportunity for younger people to talk to veterans while they were still around.
"It's a great way to start an Anzac Day, to remember with everybody else that comes to a dawn service. It's really where the whole Anzac Day resurgence is going, with younger and younger people."
Dr Clarke said Anzac Day could be difficult for veterans, but they were heartened by the community support.
"Each year they come along and there's fewer and fewer of their comrades there. But the one thing that they really do get some comfort from is seeing the families there, seeing the next generations, because it ensures that we will not forget them."
In Auckland, the crowd of more than 10,000 far exceeded the expected turnout.
Mr Key and Labour leader David Shearer attended the service, after which Mr Key was due to fly to Wellington to attend the national service.
Twelve-year-old Stephanie Davis said she had been moved by the service and was there to remember relatives who had died in World War I.
In Wellington, the dawn service opened with the loud report of a canon and a cloud of smoke that lingered around the Cenotaph, bathed in golden light, as a solo piper played.
The crowd huddled in darkness as Chaplain Peter Savage led a moving prayer that paid tribute to the three New Zealand soldiers who have died overseas since last Anzac Day.
"On this Anzac Day there would be so much that we would rather forget, but we dare not forget," he said.
"We dare not forget the tragic deaths of three brave New Zealand servicemen since last we met in this way - Corporal Douglas Grant, NZ SAS, Lance Corporal Leon Smith, NZ SAS, Corporal Douglas Hughes, 1st RNZA."
Corporal Grant and Lance Corporal Smith were killed last year in separate operations, while Corporal Hughes died suddenly in Afghanistan earlier this year.
The National Anzac Day Commemorative Service has been held in Wellington.
It began at the Tomb of the Unknown Warrior, where a dawn to dusk vigil is being held, and was followed by a wreath-laying ceremony at the Cenotaph in Lambton Quay.
In Christchurch, the crowd braved the bitter cold at a ceremony attended by Sir Jerry at Cranmer Square.
A temporary Cenotaph was constructed from pieces of rubble from throughout the city. It was put together by urban search and rescuers, whose ties to the city were forged in the days after last February's deadly earthquake.
Dr Clarke, who attended the Christchurch service, said the turnout there was growing again, with many thousands at the gathering.
"The whole whole spirit of Anzac has been shown in this city. It was a beautiful dawn here and those numbers are up," he said.
Air Force fly-bys marked the end of dawn services in many centres, with a Hercules plane flying over Auckland services and Iroquois helicopters flying over Otaki, Feilding, Palmerston North, Bulls and Foxton.
Some 400 Defence Force personnel will be serving overseas on operations, UN missions or participating in exercises during Anzac Day.
In Afghanistan, the Defence Force's Provincial Reconstruction Team will hold dawn services at its headquarters and forward bases in Bamiyan province.
The team's commanding officer, Lieutenant Colonel Pete Hall, said the personnel would reflect on those who had made the ultimate sacrifice in the service of their countries.
"It is especially poignant for those of us serving in Afghanistan as we will be remembering those who have been killed in action or died whilst deployed here."
At Gallipoli in Turkey, more than 10,000 people were expected to attend the Australian-led dawn service, followed by an Australian service at Lone Pine and a New Zealand service at Chunuk Bair.
The official New Zealand contingent will include Defence Force vice chief Rear Admiral Jack Steer, RSA president Don McIver, Defence Force personnel and representatives from Veterans' Affairs.
New Zealanders also turned out for dawn services in Australia, with representatives from the New Zealand Defence Force attending more than 40 Anzac celebrations.
In London, up to 3500 people were expected at a New Zealand-led dawn service at Hyde Park Corner, which would be followed by a wreath-laying at the Cenotaph in Whitehall and a noon service at Westminster Abbey.
This Anzac Day marks the second since a Defence Force Iroquois helicopter crashed in low cloud at Pukerau Bay, north of Wellington, on its way to a dawn flyover in the capital.
Pilot Flight Lieutenant Hayden Madsen, 33, co-pilot Flying Officer Daniel Gregory, 28, and crewman Corporal Ben Carson, 25, were killed in the crash.
Sergeant Stevin Creeggan, 37, survived but suffered serious injuries.
