New Zealand Prime Minister John Key said on Tuesday that at least 65 people were killed in the 6.3 magnitude earthquake in South Island city of Christchurch earlier in the day.

John Key arrived in Christchurch on Tuesday afternoon after an emergency cabinet minister meeting in Wellington. He said it was " the darkest day" in New Zealand history. 

TV grab taken on Feb. 22, 2011 shows people evacuating from a quake-damaged street in Christchurch, New Zealand. A massive 6.3 earthquake hit New Zealand South Island's largest city of Christchurch for the second time in less than six months, causing multiple deaths and widespread destruction. [Xinhua]

The quake on Tuesday was centered 10 km south-east of the South Island city and struck at 12:51 p.m. (2351 GMT Monday).

Police have confirmed fatalities at several locations in the city, including two buses crushed by falling buildings.

Police said other reports include multiple building collapses, fires in buildings in the central city and persons reported trapped in buildings.

Several aftershocks struck the city during the afternoon, with the largest aftershock measured at 5.7 on the Richter scale, at 1: 04 p.m..

New Zealand National Civil Defence Controller David Coetzee said the damage is worse than the 7.1-magnitude quake on Sept. 4 last year.

People have thronged onto the streets of the city center. There are fresh piles of rubble everywhere.

Residents in Christchurch were being asked to stay off the roads to allow emergency services to get through.

The quake was centered in the town of Lyttelton. Fire service said 60 percent of Lyttelton's buildings in the main road, London Street, have fallen.

The military is helping with the search and rescue operation, with the navy vessel HMS Canterbury in port and the army also helping. Port Lyttelton and the Lyttelton Tunnel are closed.

Christchurch Airport is closed, and power is out to about 80 percent of Christchurch.

Christchurch Mayor Bob Parker has declared a local state of emergency.