A radio broadcaster has been widely praised as a national hero after keeping her cool on air during a 7.5-magnitude earthquake.

Radio New Zealand journalist Vicky McKay calmly finished her midnight news bulletin when tremors rocked the seaside Cheviot town on the South Island.

Loud rumblings threatened to drown out her voice as she talked about cricket and signed off at 12.04am.

“Yes, Wellington, we are undergoing a fairly dense earthquake,” said Mrs McKay.

“Please, just get to somewhere where you are safely under some protection, because this is long and rolling, and it has been getting worse every five minutes.

“I can honestly say I doubt that I’ll be able to stay in the chair for much longer.

Powerful earthquake strikes New Zealand's South Island

“It’s definitely the worst earthquake we’ve had in Wellington for some time.”

Just before strolling seamlessly into a song, she said: “I sincerely hope that you’re all OK.”

At least two people have died after the earthquake, measured as highly as 7.8 on the Richter scale, triggered a series of aftershocks.