An earthquake measuring 6.5 on the richter scale has shaken parts of New Zealand.

The quake centred 20km east of Seddon in the Cook Strait and about 17km deep was strongly felt in Wellington, Marlborough and surrounding areas.

The quake, which struck at about 5.10pm (1510 AEST) on Sunday, follows a magnitude 5.7 on Friday and a 5.8 on Sunday morning.