The New Zealand dollar was shaken and dropped for the first time in five days after an earthquake hit the city of Christchurch, destroying parts of the central business district and cutting off some telecommunication lines connecting the city.

According to some compiled reports from different news agencies, as of 4PM (NZ time), search and rescue teams from the cities of New Plymouth and Auckland will arrive to help in the rescue and relief efforts in Christchurch.

Civil Defence Minister John Carter said the government will give all the support that is needed.

Telecoms New Zealand said in a statement that they working intensively to understand which services have been affected by today's earthquake and get these restored as soon as possible. People are advised to text or use the SMS service as significant call overload is now experienced throughout the country.

Minister Carter added: "But immediately people need to make sure they are safe, make sure their families are safe...that their friends and families are all taken care of.

People should where possible move out of the area where there is significant damage, in the city centre, and longer-term people should look to leave the city. There will be a continuous series of aftershocks and for those who have lived through the last few months that would be traumatic."

Christchurch Hospital has suffered "reasonably minimal damage" and is open.

Air ambulances have transported some patients to other centres and other South Island hospitals are clearing their capacity so they can take casualties if needed.

The government had been assured by Transpower that they have the grid up and running again after power went out to parts of the city.

Christchurch airport remains closed but runways are being assessed.