The nation has marked the one-week anniversary of Christchurch's devastating earthquake with thousands gathering at churches and squares across the country.

The 6.3 magnitude quake struck at 12.51pm on February 22, and today mourners gathered at churches and town squares all around the country to mark the moment.

Hundreds of people from outside the city have arrived to help with the massive clean up operation, including around 200 farmers who manned 20 diggers to clear more than 1100 tonnes of silt from the New Brighton area yesterday.

Cathedral bells tolled in city centres as the nation stopped for a two-minute silence.

Some people cried, while others hugged each other for support.

A short ceremony in front of the Christchurch Arts Centre began and ended with waiata.

Bishop Victoria Matthews offered prayers for both the dead and the living.

Dean Peter Beck then read the 23rd Psalm, and Bishop Victoria concluded with a Trinitarian blessing.

Search and rescue workers in quake-torn Christchurch downed tools and joined the rest of New Zealanders standing in silence.

Prime Minister John Key, who had called for the national period of silence, was among those at the Christchurch Arts Centre. 

He was accompanied by his wife, Bronagh, and Christchurch Mayor Bob Parker.

The death toll from the quake is likely to be around 240, police said today. The confirmed number of dead rose to 154 overnight.

The silence across the nation, including some of the country's busiest workplaces, was a poignant sign of unity for the people of Christchurch and respect for those who lost their lives.

Up to 5000 people gathered on the lawn and forecourt of Parliament at 12.30pm to join Governor-General Sir Anand Satyanand and Lady Satyanand, Deputy Prime Minister Bill English, church and faith representatives, MPs and overseas diplomats.

For 10 minutes after the silence, the Cathedral of St Paul near Parliament rang its bells in a half-muffled peal to acknowledge those who had lost their lives.

In Auckland, the silence came during an ecumenical service at Holy Trinity Cathedral, attended by leaders of city churches, Mayor Len Brown and local MPs, and about 750 other Aucklanders.

From the lectern, Len Brown said he had a message for Christchurch:

"Auckland has never been closer to you.

"We have never been more willing to do everything we can to help.

"And we will do whatever we can to help.

"We will give you homes away from the danger to recuperate in; we will give you money to help feed and care for those who have lost so much. We do give you respect for the people you have lost; and we do give you our love.

"We are in awe of your spirit, of your courage and selfless acts of altruism in the face of tragedy."

Emotions ran high in Hamilton, where the silence was broken by the sobs of a woman among the crowd at the Cathedral Church of St Peter.

In Dunedin thousands turned out to pay their respects.

In a moving tribute, Mayor Dave Cull sent a message of support to "Christchurch, our big sister up the line''.

Meanwhile, Kiwis have so far contributed more than $14 million to relief funds.