Huge chunks of ice have broken off the Tasman Glacier, New Zealand’s largest.

They have filled up at least a quarter of the Meltwater Lake at the foot of the glacier in the Aoraki/Mount Cook National Park, reports say.

The lake started to form in the 1970s as the glacier rapidly retreated – a phenomenon thought to have been largely caused by global warming.

One guide says the chunks resemble huge skyscrapers lying on their side in the water.

Another two local guides were alerted to the event early on Wednesday morning.

A tidal surge up to two metres (6.5ft) high damaged a lake jetty and lifted a boat trailer upside down onto another trailer.