Wellington, July 15 (DPA) A powerful earthquake estimated between 6.6 and 8.2 on the Richter scale rocked southern New Zealand Wednesday, forcing authorities to issue a tsunami warning.

New Zealand seismologists said the temblor measured 6.6 but reports from the US Geological Survey said it was 7.8 and another measurement put it at 8.2, according to a local civil defence official.

'An earthquake of this size has the potential to generate a destructive tsunami that can strike coastlines in the region near the epicentre within minutes to hours,' the Pacific Tsunami Warning Centre in Hawaii said in an e-mail alert.

Residents in the Southland and Otago provinces were told to listen to their radios after the Pacific Tsunami Warning Centre in Hawaii issued an alert.

The quake was centred 90 km southwest of the lakeside resort town Te Anau in Fiordland, but was felt 300 km away in Dunedin, Radio New Zealand reported.

With a focal depth of only five kilometres below the surface, it shook items off the shelves of supermarkets in Queenstown, toppled ornaments and cracked walls, but there were no immediate reports of serious damage.