A huge earthquake has struck Canterbury with witness reporting the 6.3 magnitude quake felt more violent than the quake in September.

GNS Science said the quake was centred at Lyttelton at a depth of 5km.

Phone lines are down and calls are not being connected to emergency services.

Twitter users have reported feeling the quake in Wellington and Dunedin.

Herald reporter Jarrod Booker said people had left buildings and were out on the street.

He said the shake lasted approximately a minute and was extremely violent - rocking buildings back and forth.

Tarmac on the roads have cracked and water mains have burst, flooding the streets, he said.

He said the carpark at the Christchurch Star had turned into a river with huge cracks and the roads had risen in areas.

People were comforting people outside amid a general state of shock as people try to absorb what had happened, he said.

Objects fell off shells.

(Source NZ Herald)