New Zealand's been hit by a tsunami, following a powerful earthquake on the south island.

The country's civil defence ministry is warning that more powerful waves may be on their way towards the country.

They are urging anyone in low lying areas along the east coast of the north and south islands to move to higher ground.

Tsunami sirens have sounded in cities including Christchurch, Canterbury and Wellington.

The quake is thought to measure between 7.5 and 7.8 on the Richter scale.

It struck about 90 kilometres north-east of Christchurch which was devastated in the 2011 quake. 

It is not known if anyone has been injured.

Christchurch residents Hugh and Emma Sintes have described what happened when the quake hit earlier: