Waters north of New Zealand are set to become one of the world's largest ocean sanctuaries, covering an area roughly the size of France, with a full ban on fishing and mining, New Zealand's Prime Minister John Key said at the United Nations on Monday.

Called the Kermadec Ocean Sanctuary, the area covers 620,000 square km (239,000 square miles) of ocean, and encompasses a string of undersea volcanoes and is home to endangered marine life including whales, dolphins and turtles.

The announcement surprised New Zealand's seafood export industry, worth NZ$1.4 billion ($882 million) a year, and will prevent mining firms gaining seabed prospecting rights.