Tsunami warning issued after quake strikes New Zealand

US Geological Survey says 7.8-magnitude earthquake has hit central New Zealand, prompting a tsunami warning.

A powerful magnitude 7.8-magnitude earthquake has rocked New Zealand, prompting a tsunami warning and knocking out power and phone services in many parts of the country.

The US Geological Survey said the shallow temblor hit 90km from the South Island city of Christchurch, which was devastated five years ago by a 6.3 tremor.

That quake killed 185 people in one of New Zealand's deadliest disasters.

Monday's earthquake, initially put at 7.4 but later upgraded, struck at 12:02am local time (1102 GMT on Sunday).