Rain doesn't stop crowds at Melbourne Anzac dawn

Crowds started to gather at Melbourne's Shrine of Remembrance hours before the dawn service to commemorate the Anzac Day centenary.

Tens of thousands of people have braved a chilly start and light showers for the service which is about to get under way.

Margaret Lugg left home at 2.30am to get a front row position to honour a relative who never made it home from Gallipoli, and her father who was a Rat of Tobruk.

"It's the young people who have made today what it is, it was never this popular when I was younger," she said.

Under a sea of umbrellas, the crowd fell silent as the service began with a verse from For the Fallen and the familiar response: "We will remember them".

Royal Australian Artillery Lieutenant and Military Cross recipient Neville Clark spoke of the sacrifice of those who have served in the spirit of Anzac since the sun rose on that first Anzac morning.

It was 100 years ago on April 25 that the world began to know what it meant to be an Australian or New Zealander, he said.

"How many great Australians there are today, still carrying on the great tradition of Anzac," he said.

Afghanistan veteran Colonel Kahlil Fegan said he often contemplated what set Anzac troops apart from others in conflicts and on peacekeeping missions.

World class training and equipment are part of it, but it's a spirit of courage, endurance, discipline, respect, larrikinism and mateship that make the difference, he said.

"What I've seen I can only describe as a manifestation of a spirit ... the same spirit that drove the original Anzacs off the boats and onto the beaches at this time 100 years ago."

Dignitaries made their way into the shrine's inner sanctum to lay wreaths and poppies.

Some members of the public followed while others made their way to St Kilda Road for the parade later on Saturday morning.