Wellington, Sep 4 (DPA) A state of emergency was declared Saturday after Christchurch, the biggest city in New Zealand's South Island, was extensively damaged by a massive 7.1-magnitude earthquake that flattened buildings, ripped up roads and cut power, water and sewage connections.

The quake, centred only 10 km underground, was one of the biggest to hit a population centre in one of the world's most earthquake-prone countries in the last century.

Miraculously, only two serious injuries were reported so far. Officials said mass casualties were avoided because the quake struck at 4.35 a.m. when most people were still asleep.

There were reports of serious damage at the port of Lyttelton, 12 km from the city centre, but no tsunami warning was issued.

Guests fled multi-storey hotels in the city centre, which was rattled by the trembler. One guest, Sue Foley, told Television New Zealand that she could not stand and was thrown back on the bed in her eighth floor room after being woken up by the shaking.

Ten sizeable aftershocks ranging from 3.9 to 5.2 on the Richter scale were recorded after the initial shake and police closed the central business district of the city of nearly 400,000 after roads were blocked by the fallen facades of office blocks.

Power was cut to most of the city and Christchurch and the entire Canterbury province, where more than 550,000 people live in mainly rural areas.

Civil defence officials said up to 1,000 residents in Christchurch's seaside suburbs may have to be evacuated due to flooding from broken water and sewage pipes. Other suburbs were flooded when the River Avon overflowed its banks as the quake struck.

All bus services were suspended in the city as metre-deep crevasses appeared in roads, the South Island rail network was shut down pending inspection of the tracks and the Christchurch International Airport closed until runways were checked.

Reports said emergency services had rescued about 10 people who were trapped in holes in the ground.

Police, who reported some cases of looting shops and businesses in the city, urged people to stay indoors and avoid using mobile phones after telecom companies were forced to switch cell sites to battery power.

Residents in the suburbs, many still in pyjamas, reportedly walked the streets in a daze, inspecting devastated houses that looked as though they had been bombed.

Civil defence minister John Carter broadcast TV appeals to people not to panic and to check on friends and neighbours to ensure they were safe.