A Russian helicopter that went down off the coast of Norway's Svalbard archipelago in the Arctic has been found and the eight people on board are presumed dead, Norwegian rescue crews said on Sunday, two days after the aircraft disappeared.

"The wreck of the Russian helicopter has been located... northeast of Heerodden, at a depth of 209 meters (686 feet). The search has now concluded, and has moved into a search phase for the presumed dead," the rescue services said in a statement.

Russian helicopter with 8 people on board has gone down at sea 2-3 kilometers off the Arctic port of Barentsburg in Svalbard, Norway's rescue service said Thursday.

A sea patrol plane, a Danish aircraft, two Norwegian helicopters and several vessels had been searching the area since Thursday.

A small robot submarine was also used to investigate an area where an oil patch and bubbles were observed.

Norway was afforded sovereignty of Svalbard, located around 1,000 kilometres (600 miles) from the North Pole, under the 1920 Treaty of Paris.

Nationals of all signatory states enjoy "equal liberty of access and entry" to Svalbard and its waters.

As a result, Russia operates a coal mine in Barentsburg, home to several hundred Russian and Ukrainian miners. The helicopter was on its way from the Pyramiden settlement to Barentsburg.

The aircraft was a Russian Mili Mi-8 helicopter belonging to Russian charter company Konvers Avia.