A huge iceberg, the world's largest, has broken off from an ice shelf in Antarctica and is floating through the Weddell Sea, the European Space Agency said.

Called A-76 and roughly the shape of Manhattan in New York but more than 70 times bigger, it was picked up on satellite images and is "currently the largest berg in the world", the ESA said.

It is around 170km long and 25km wide, with an area of 4,320sq.km.

The iceberg, which broke off the western side of the Ronne Ice Shelf, was originally spotted by the British Antarctic Survey and confirmed using images from the Copernicus satellite.

It takes the place as the world's largest from the A-23A iceberg - approximately 3,880sq.km in size - which is also in the Weddell Sea.

Last November, what was then the world's largest iceberg appeared to be on a collision course with a remote South Atlantic island home to thousands of penguins and seals, threatening to impede their ability to gather food.

The iceberg, known as A68a, had also broken off from the Larsen Ice Shelf, which has warmed faster than any other part of Earth's southern most continent.

A68a, which was 160km long and 48km across, broke up before it could cause any damage to the abundant wildlife in the British Overseas Territory of South Georgia.

Earth's average surface temperature has gone up by one degree Celsius since the 19th century, enough to increase the intensity of droughts, heat waves and tropical cyclones.

But the air over Antarctica has warmed more than twice that much.

Icebergs are traditionally named from the Antarctic quadrant in which they were originally sighted, with a sequential number.

If the iceberg breaks, a sequential letter is added.

The Ronne Ice Shelf near the base of the Antarctic Peninsula is one of the largest of several enormous floating sheets of ice that connect to the continent's landmass and extend out into surrounding seas.

Periodic calving of large chunks of those shelves is part of a natural cycle, and the breaking off of A-76, which is likely to split into two or three pieces soon, is not linked to climate change, said Ted Scambos, a research glaciologist at the University of Colorado.

Mr Scambos said the Ronne and another vast ice shelf, the Ross, have "behaved in a stable, quasi-periodic fashion" over the past century or more.

Because the ice was already floating in the sea before dislodging from the coast, its break-away does not raise ocean levels, he said.

Some ice shelves along the Antarctic peninsula, farther from the South Pole, have undergone rapid disintegration in recent years, a phenomenon scientists believe may be related to global warming, according to the US National Snow & Ice Data Center.