23:13 (GMT+4) New Zealand Prime Minister John Key said two people were killed in a powerful earthquake that the struck the Pacific nation early on Monday, Reuters reported.
"We don't have any indications at the moment to believe it will rise, but we can't rule that out," Key told reporters in Wellington, adding that details of the casualties were still being confirmed.
Key said a military helicopter was being dispatched to the coastal tourist town of Kaikoura, near the epicenter of the 7.8 magnitude quake, some 91 km (57 miles) north-northeast of Christchurch in the South Island.
18:01 (GMT+4) The earthquake measured at 7.9 on the Richter scale struck New Zealand's South Island, the European-Mediterranean Seismological Center (EMSC) said on Sunday, Sputnik International reported.
The 7.9-magnitude earthquake hit the island at 11:02 GMT, EMSC specified.
The epicenter of the earthquake was less than 120 miles from the city of Christchurch that was heavily damaged and saw at least 185 deaths in the earthquakes of 2010-2012.
There have been damages to residential buildings, but so far no reports of casualties, according to some local media outlets.
New Zealand's Civil Defense and Emergency Management Ministry (MCDEM) issued a warning for a tsunami for the eastern coast of both North and South Islands.
"The tsunami threat is for the east coast of all New Zealand (including Christchurch, Wellington and the Chatham islands," MCDEM twitted.
The instructions for behavior during quakes and tsunami and advised everyone on the eastern coast to "move to high ground," the ministry added.