Authorities in New Zealand say they have been hit by five severe earthquakes over the space of four hours, with thousands fleeing their homes.
A tsunami warning is in force, with waves predicted to reach five metres high.
TV New Zealand reports that one person has died of a heart attack in Christchurch.
There are also reports of casualties at Kaikoura on the South Island where two metre-high waves followed the largest 7.8 magnitude quake.
Dawn has now broken and rescue helicopters are hoping to assess the damage more accurately from the air.
As yet there are no reports of any Irish casualties.
The seismic activity knocked out New Zealand's emergency call number, 111, for about 10 minutes, police reported.
It caused items to fall from shelves and windows to break in Wellington, and forced hundreds of tourists onto the streets as hotels were evacuated.
There are no reports of any Irish casualities following today's earthquake and tsunami in New Zealand.
A series of earthquakes and aftershocks have hit the country. One of them generated a tsunami wave around six feet high on South Island.
The largest quake was 7 point 8 magnitude and hit just after midnight local time.
The Department of Foreign Affairs here has said it has not received any requests for assistance, but is continuing to monitor the situation.
The local Fire Department is dealing with emergency calls in the town of Christchurch, New Zealand, following the quake but, as yet, officials say there are no reports of serious damage, injuries or fatalities.
Damage to a Nelson City supermarket following #eqnz #NewZealand pic.twitter.com/vQcuM9J1WG
— Donie O'Sullivan (@donie) November 13, 2016
A powerful earthquake has generated a tsunami in New Zealand, with the first waves hitting the South Island, government officials have said.
The department of civil defence warned people all along the country's east coast to move to higher ground.
The ministry had earlier sent out a message on Twitter saying there was no tsunami threat to the country.
It then sent out another message - "situation has changed - tsunami is possible" - before reporting that a tsunami had, in fact, hit.
A tsunami has been generated, the first wave has arrived in the North Eastern Coast of the South Island. #eqnz
— National Emergency Management Agency (@NZcivildefence) November 13, 2016
The magnitude-7.8 quake struck in the early hours of Monday near the city of Christchurch. It was at a relatively shallow depth of six miles.
Some minor damage was reported in the capital, Wellington, more than 120 miles away. The streets of inner city Wellington are thronged as thousands of citizens evacuate.
There were no immediate reports of major damage or injuries in Christchurch.
A powerful earthquake has struck New Zealand near the city of Christchurch, with strong jolts felt more than 120 miles away in the capital Wellington.
There were no immediate reports of major damage or injuries and there was no immediate danger of a tsunami, according to the Pacific Tsunami Warning Centre.
The 7.4-magnitude quake struck just after midnight on Sunday and was centred 57 miles north-east of Christchurch, according to the US Geological Survey.
It was at a relatively shallow depth of six miles.
Earthquakes tend to be more strongly felt on the surface when they are shallow.
New Zealand sits on the "Ring of Fire," an arc of seismic faults around the Pacific Ocean where earthquakes are common. An earthquake in 2011 in Christchurch killed 185 people.
New Zealand sits on the "Ring of Fire", an arc of seismic faults around the Pacific Ocean where earthquakes are common.
- AP