A powerful earthquake has hit the South Island of New Zealand, causing some damage but there are no reports of fatalities.

The 7.4 magnitude earthquake occured at 4.35am local time, according to the US Geological Survey.

The epicenter of the quake was located 4 miles southeast of Christchurch at a depth of 6 miles, the US Geological Survey reported Friday, correcting an earlier report that put the depth much deeper.

The shallow level of the earthquake meant the initial quake and its after shocks were particularly violent.

There have been reports of damage to many buildings while some have collapsed entirely and localised parts of the city have been flooded.

The Christchuch police have warned residents that it is unsafe to be outside as extensive looting has occured in commercial areas.

A tsunami alert was not issued immediately following the quake.