Christchurch, Nov 14 (AFP): Residents in coastal areas of New Zealand fled through the night on Monday after a powerful 7.8 earthquake struck just after midnight, triggering a potentially destructive tsunami.

Nearly seven hours after the first quake struck, Prime Minister John Key confirmed two fatalities, saying “we cannot rule out” that number will rise.

“At this point we are unable to give precise details of what caused those fatalities,” Key said, adding that communication problems made it difficult to get information from the affected areas of the South Island.

As tsunami warning sirens were activated in South Island coastal towns and along the east coast of the North Island, police and emergency workers went door-to-door to evacuate seaside properties.

A “destructive tsunami" with waves up to five metres (16 feet) was possible, the ministry of civil defence, responsible for emergency management in New Zealand, said in a bulletin.

Some early waves were up to two-metres but civil defence warned they could intensify and described the tsunami as “an event of life-threatening or national significance”.

Civil Defence Minister Gerry Brownlee told a media briefing he had received reports of casualties near the South Island coastal town of Kaikoura but details were unclear.