CHRISTCHURCH, New Zealand (AFP) – New Zealand authorities extended a state of emergency in earthquake-hit Christchurch Monday and said the centre of the country's second largest city remained a no-go zone.

Authorities said strong aftershocks continued to rock Christchurch following the 7.0-magnitude quake on Saturday, which caused extensive damage estimated at two billion dollars (1.44 billion US).

Police and troops manned roadblocks sealing off the city centre, with the Civil Defence authority saying the area remained closed due to danger from falling masonry and glass.

"The state of emergency has been extended until midday Wednesday," a ministry spokesman told AFP.

Schools, shops and businesses were closed and residents were advised to stay at home until inspections of the more than 500 buildings damaged in the country's most destructive quake for almost 80 years were completed.

Officials warned it would be some time before life returned to normal in the city of 340,000 people.

"This isn't a short-term thing," said Prime Minister John Key, who was scheduled to hold a cabinet meeting Monday to fast-track arrangements to restore Christchurch's damaged infrastructure.

Key is expected to appoint a special commissioner to oversee rebuilding efforts.