By Greg Wood

CHRISTCHURCH, New Zealand, Sept 6, 2010 (AFP) - The rubble-strewn heart of Christchurch resembled a ghost town Monday as troops took control of the city centre to enforce a no-go zone in the wake of Saturday's 7.0 magnitude earthquake.

"It's a strange sight, just absolutely eerie and very quiet," Christchurch hotelier Anna Crighton said from her bed-and-breakfast on the fringe of the central business district.

"There's hardly anyone around and no cars. I can look out of my window and just see a pile of rubble in the middle of the road."

The regular Monday morning bustle in New Zealand's second largest city was absent after officials extended a state of emergency until Wednesday and told workers to stay out of the town centre.

Uniformed soldiers manned checkpoints leading into the inner city, while army and police helicopters using a local park as a temporary airbase buzzed overhead as they carried out aerial damage reconnaissance .

School playgrounds across Christchurch and the neighbouring districts of Selwyn and Kaiapoi were silent, with classrooms deemed unsafe until structural engineers complete damage assessments.

Retailers were among the few people allowed into the city centre, not to open their businesses but to check if their shops were salvageable.

Bookshop owner Barry Hancox said he had a lucky escape after last month relocating his business from a shop where it had operated for more than 50 years, which was wrecked in the tremor.

"It's amazing, timing's everything," he told Sky News, noting much of his old shop had been reduced to rubble while premises a few doors along were untouched.

Three days after Saturday's pre-dawn quake, residents were still being advised to boil drinking water because of the risk of contamination and about 200 people whose homes were uninhabitable were sheltering in welfare centres.

"There's a lot of people out there who are hurting," police inspector John Price said.

Urging residents to check on their neighbours and friends, Price said it was too early to say when life in the city would return to normal.

"We need to make sure people are safe when they go back into that environment," he said.

Crighton said her 1892-built property was relatively unscathed because it had been earthquake-strengthened a few years ago but she was "heartbroken" at the devastation suffered by some of the old buildings that gave the city its character.

"We seen overseas, where people have rushed to demolish after widespread devastation and we can't let that happen here," she told AFP.

One of the properties under threat is the sprawling Deans homestead on the Canterbury Plains, owned by relatives of Wallabies coach Robbie Deans, where the 2005 film "The Lion, the Witch and the Wardrobe" was filmed.

Sections of the brick-built dwelling's walls collapsed when the quake hit, leaving the roof teetering precariously.

"It is a miracle that they all got out alive,' neighbour Gillie Deans told the Australian newspaper. "Nature can be such a bitch."