Thousands stood in silence at the first anniversary service for the 29 men who remain entombed in the Pike River mine.

The moment of silence took place at exactly 3.44pm, the time of last year's first explosion.

Heads bowed, shoulder to shoulder, the victims' families stood together in honour of the 29 men as their photographs were displayed on a huge screen.

To complete the service, family members and the Greymouth community placed a piece of coal into the back of a Chevy truck to symbolise letting go of some of the pain.

The truck was owned by one of the miners and its number plate reads "our 29".

Earlier, families' spokesman Bernie Monk received a standing ovation after he addressed the crowd.

"Whatever happens here we are going to fight till the end until we get our guys out," he said.

Mr Monk asked for the support of the community for the "long journey ahead".

He said the Pike River families had been braced by the community for the past year and would not have survived without its support.

"The people of the West Coast, I ask you from the bottom of my heart to keep supporting the families."

Mr Monk told the crowd that when he visited Pike River mine this morning he saw his son's face as he looked into the portal.

"We are going to make sure this doesn't happen again and we want your support," he concluded.

After Mr Monk's address, the daughter of a lost Pike River miner took the stage and sang In the Arms of an Angel in memory of her dad, Milton Osborne.

Carol Rose, Stuart Mudge's mother, accompanied her on guitar.

About 250 family members were seated at the front of the crowd.

A display of 29 blue miners' helmets lay before the Pike River families.

Lawyers and counsellors from the Royal Commission investigating the disaster could be seen within the crowd at Greymouth's Rugby Park.

Prime Minister John Key and Labour leader Phil Goff were seated on the stage.

Earlier, a granite stone memorial bearing the names of the 29 men entombed in the mine was unveiled in Greymouth.

Mr Key, Grey District Mayor Tony Kokshoorn and former chief mines inspector Harry Bell presented the memorial to family members on the first anniversary of the tragedy.

The stone is surrounded by 29 red roses and 29 white roses.

About 200 Pike River family members applauded when the memorial was unveiled.

Some family members, wearing T-shirts bearing a photograph of their loved one, shook the Prime Minister's hand.

Before it was unveiled Mr Kokshoorn said: "This is a symbol of our men that are still lying up there in the mine."

Chief former mines inspector Harry Bell was applauded by the families when he promised he "would not rest" until the bodies were recovered.

A poem engraved into the back of the memorial was read out to the families as they stood in silence on Greymouth's main street.