An expedition in August and September charted the islands, which have yet to be named and were previously hidden under glaciers, said the head of the northern fleet, Vice Admiral Alexander Moiseyev.

"Mainly this is of course caused by changes to the ice situation," Moiseyev, who headed the expedition, said at a press conference in Moscow.

"Before these were glaciers; we thought they were (part of) the main glacier."

"Melting, collapse and temperature changes led to these islands being uncovered."

Glacier loss in the Arctic in the period from 2015 to 2019 was more than in any other five-year period on record, a United Nations report on global warming said last month.

Russia has opened a string of military and scientific bases in the Arctic in recent years, with interest in the region growing as rising temperatures open up shipping routes and make hitherto inaccessible mineral resources easier to exploit.

This summer's expedition to two archipelagoes -- Franz Josef Land and Novaya Zemlya -- involved some 60 people including civilians from the Russian Geographic Society and was the first aboard a rescue towboat instead of an icebreaker.

Video of expedition members encountering an angry walrus that attacked their inflatable landing craft went viral last month.

"The two months this year when we held our expedition to Franz Josef Land can be described as warm," said Denis Krets, commander of the northern fleet's expedition force.

"We were very lucky because we could land on islands where not every year the shore and the inshore water is free of ice."

During the expedition, the defence ministry announced it had found five new islands in Vize Bay off Novaya Zemlya, a vast mountainous archipelago with two main islands.

The islands had previously been seen on satellite images but the expedition was the first to see them.

It also said it had also confirmed the existence of an island that had been previously mapped as a peninsula of Hall Island, part of the Franz Josef Land archipelago, west of Novaya Zemlya.

Moiseyev said names for the new islands were "upcoming".

"Of course each island will receive a name but first you have to lay out the case for it."