WELLINGTON (AFP) - A strong 6.9-magnitude earthquake struck off New Zealand on Sunday, jolting the nation's capital but no tsunami alert was issued and there were no immediate reports of damage.

The quake hit at 5:09 pm (1.09pm Singapore time) 57 kilometres south-southwest of Wellington at a depth of 10.1 kilometres, the US Geological Survey said.

It was followed minutes later by another quake of 5.5 magnitude and came about 10 hours after a 5.8 tremor in the same region which has been hit by multiple quakes in recent days.

New Zealand's GeoNet earthquake monitoring service described the 6.9 tremor which was felt widely as "severe".

"There was a rocking and rattling which lasted about 30 seconds," a resident in the resort town of Nelson told AFP.

Recent quakes have been centred about 200 kilometres north of New Zealand's second largest city Christchurch, where a 6.3-magnitude quake in February 2011 toppled buildings onto lunchtime crowds, leaving 185 people dead.

The country sits on the so-called "Ring of Fire", the boundary of the Australian and Pacific tectonic plates, and experiences up to 15,000 tremors a year.