Image copyright Getty Images Image caption The waters surrounding New Zealand are rich with marine biodiversity, including sea lions, dolphins and turtles

New Zealand has revealed plans to turn an area of the South Pacific about the size of France into a marine reserve.

The Kermadec Ocean Sanctuary lies north of the mainland and includes a chain of islands and underwater volcanoes.

Prime Minister John Key made the announcement at the United Nations General Assembly in New York.

Fishing and mining will be banned in what Mr Key called "one of the most geographically and geologically diverse areas in the world."

"New Zealanders value our coasts and oceans, which are an important part of our culture, economy and environment and we are committed to managing them sustainably," he said in a statement.

The government is aiming to pass legislation to create the marine reserve next year.

'No forewarning'

The area to be protected is a vast 620,000 sq km (239,400 sq miles) stretch of the South Pacific, about 1,000km north-east of North Island.

It contains the 10-km deep Kermadec trench, one of the deepest ocean trenches in the world, and is rich in sealife including whales, dolphins, endangered turtles and sea birds.

Image copyright Pew Environment Group Image caption The Kermadec marine reserve (highlighted by the red dotted line) includes a number of islands and underwater volcanoes (denoted by the triangles)

The move was welcomed by environmentalists.

Pew Environment Group, one of several groups which had lobbied for the creation of the reserve, said it effectively expands New Zealand's protection of its marine environment from 0.5% to 15.5% of its marine spaces.

"It's an extraordinary achievement for all New Zealanders and for the people of the Pacific Islands," Pew's campaign director Bronwen Golder told the BBC.

But the announcement has surprised fishing and mining companies.

George Clement, chairman of Seafood New Zealand, told Reuters news agency they had had "no forewarning from government" and that the industry "needs time to consider the full implications".