Shocks rock NZ overnight

We have chosen to take a cautious approach at this stage to ensure public safety,", Civil Defence controller Michael Mendonca told the New Zealand Herald.

The barriers in the CBD were supposed to have been lifted at 5am local time.

Shortly after midnight, the paper reports, a shock of 4.3km struck, while just after 7am local time the earth shook with an aftershock of between 4.5 and 4.6 on the Richter scale.

Also overnight, two sizeable earthquakes have rocked Hawke's Bay, on New Zealand's North Island.

A 5.3-magnitude quake hit at 4.18pm (1418 AEST) on Thursday, centred at a depth of 20km, 10km southeast of Porangahau and 80km south of Hastings.

A tremor measured at 4.3 followed at 8.25pm (1825 AEST), centred at a depth of 25km, 20km southeast of Porangahau.

There were no reports of damage or injury in either quake, but they were felt widely.

"I was on the third floor and I can tell you it was rocking," a Hastings police spokesman told NZPA after the first one.