Tourism New Zealand has stressed that the country remains “open for business” despite a massive earthquake that struck Christchurch over the weekend.

The tourist board’s chief executive Kevin Bowler warned against all but essential travel to Christchurch, where a state of emergency has been declared, but said that the rest of the country had been unaffected and tourism was continuing normally.

Christchurch, the largest city on the Southern Island, was hit by a 7.1 magnitude earthquake on Saturday morning, which caused the ground to shift by up to 11 feet, and was larger than the one that killed 200,000 people in Haiti earlier this year.

Much of the city centre remained sealed off and under curfew for a second night on Sunday.

More than 500 buildings have been badly damaged. Two men were seriously hurt by falling masonry but there have been no reports of deaths.

Gale-force winds tearing at unstable structures were adding to fears of collapse, whilst heavy rains had swollen rivers and pose a serious threat to the town.

Plans were being drawn up to evacuate residents from the town of Waimakariri, north of Christchurch.

John Key, the Prime Minister, who grew up in Christchurch, said: “Parts of the city look like they have been put in the tumble dryer and given a darn good shake.

“You can see utter devastation.”

Strong aftershocks continued to terrify residents as they struggled to come to terms with the extensive damage suffered by their city.

A big clean-up has already started, with bulldozers scooping up the fallen masonry that litters streets.

Damage is estimated to cost billions of dollars and will take years to repair.

The last major earthquake to strike the South Island, a magnitude 7.8 tremor that hit the sparsely populated Fiordland region on July 16, 2009, moved the southern tip of the country 12 inches closer to Australia.