WELLINGTON - Residents in New Zealand were warned Friday to be prepared for a civil emergency as strong aftershocks continued to rock the region two days after a powerful 7.8 earthquake.

At least 11 tremors with a magnitude of more than five, including one of 6.1, have hit the region since Wednesday night's initial shake off Fiordland in the southwestern part of the country.

Regional civil defence controller Neil Cruickshank said the aftershocks were a normal consequence of a magnitude 7.8 quake but he warned people in southern districts not to be complacent about the apparent lack of widespread damage.

"The scientists are still considering what combination of geographical and geological factors have influenced the impact of this particular earthquake," he said.

"People in coastal communities need to be aware that the quake did generate a small tsunami on Wednesday night and that the potential for a damaging tsunami exists with every large earthquake."

More than 14,000 earthquakes are recorded annually in New Zealand which sits in the Pacific "Ring of Fire" earthquake zone.

In 1931 a 7.8 tremor killed at least 256 people in the North Island city of Napier.

Because of the remoteness of the latest earthquakes the Earthquake Commission received more than 500 claims but none was for major damage. "

They're all still looking very small - things like ripped wallpaper and cracks in the ceiling and outside walls," commission spokesman Lance Dixon said.