Prime Minister John Key has asked all New Zealanders to observe two minutes' silence from 12.51pm on Tuesday, exactly one week after Christchurch's deadly earthquake, to honour quake victims.

2 Minutes Silence in respect for the Christchurch Eartquake victims

Mr Key has said Tuesday's earthquake may be New Zealand's single most tragic event in its history.

"I am calling on all New Zealanders to stop and remember those who have lost their lives, those who are missing, and the hundreds of people who are mourning family and friends," he said.