WELLINGTON (AFP) - A strong 5.6-magnitude earthquake hit New Zealand's South Island on Monday, with local authorities saying it shook buildings but caused no serious damage.

The tremor struck at 2.29 pm local time (10.29am Singapore time) at a relatively shallow depth of 10 km, with its epicentre about 30 km north-west of Wanaka, the US Geological Survey (USGS) said.

New Zealand's official GeoNet monitoring service listed the quake as "severe" and said there were reports of strong shaking from across the lower South Island, but added that it occurred in a sparsely populated region.

"Due to the distance from populated centres, it is not expected to be greatly damaging," it said.

Wanaka-based Otago Daily Times reporter Lucy Ibbotson said her office building shook for about 40 seconds. "We were panicked, the intensity seemed to build up," she wrote on the newspaper's website.

Wanaka police said the quake caused "a small number of broken windows and no major reported incidents".

New Zealand is on the boundary of two tectonic plates and experiences up to 15,000 tremors a year, most so minor they are not noticeable. But a devastating tremor hit the South Island city of Christchurch in February 2011, killing 185 people.

There have been two other large tremors in the country in recent weeks, including a 5.9-quake at the top of the South Island, neither of which caused any damage or injuries.