Wellington, Aug 16 (IANS): A series of strong earthquakes jolted New Zealand Friday, the government's GeoNet monitoring service said.

The first quake with a 6.6-magnitude, struck at 2.31 p.m. and was centred 10 km southeast of Seddon, at a depth of 8 km, Xinhua reported.

The quake was earlier reported at magnitude 6.2, but GeoNet later updated the measurement. Meanwhile, the US Geological Survey reported that the earthquake was measured 6.8 on the Richter scale.

There was a series of strong aftershocks, measuring from magnitude 4.2 to magnitude 5.8, which followed over the next hour, all centred in the same vicinity.

One of the main highways out of Wellington was blocked by a rockfall and train services were suspended.

Inspector Pete Cowan, of Wellington district police, urged people to be patient.

"There is significant traffic on city centre roads and many people walking home and we ask people to take extra care," Cowan said in a statement.

The Wellington Region Emergency Management Office said it had received no reports of major structural damage.