A harness recovered from an unusually friendly white whale in north Norway may indicate the animal had been trained by the Russian navy as part of a marine mammal special force, experts have said.

The beluga whale was first sighted last week in waters off Finnmark – Norway’s most northerly county which borders Russia.

“We were going to put out our nets when we saw a whale swimming between the boats,” 26-year-old fisherman Joar Hesten told Norwegian public broadcaster NRK.

Fishers said the whale had repeatedly sought them out, and they spotted it had a harness on which it was apparently trying to rub off against the hulls of their boats.

After several failed attempts by the Norwegian Directorate of Fisheries, Mr Hesten was able to remove the two straps attached to the animal late on Friday.

Tragic photos show beached whales Show all 15 1 /15 Tragic photos show beached whales Tragic photos show beached whales A dead sperm whale lies on Hunstanton beach in Norfolk on 5 February 2016 AFP/Getty Tragic photos show beached whales Volunteers pour buckets of water over the 80 remaining live pilot whales found stranded on remote Ocean Beach on New Zealand's southern-most Stewart island, 8 January 2003 AFP/Getty Tragic photos show beached whales Contractors clear away the body of one of the dead 48ft sperm whales that were washed-up on a beach near Gibraltar Point in Skegness, Lincolnshire in 2016 PA Tragic photos show beached whales People pass by a beached whale at the Pointe de la Torche, near Brest in France on 29 November 2011 AFP/Getty Tragic photos show beached whales A woman touches the tail of a large whale carcass on Wattamola Beach at the Royal National Park in Sydney on 25 September 2018 AFP/Getty Tragic photos show beached whales Beached humpback whale in California, 2015 AFP/Getty Tragic photos show beached whales Dead long fin pilot whales at Hamelin Bay on Australia's west coast on 23 March 2009 AFP/Getty Tragic photos show beached whales A 36ft sperm whale lies dead on the beach at Sutton Bridge, in The Wash, off the Lincolnshire coast, where it became stranded in 2004 PA Tragic photos show beached whales A female fin whale opens its mouth as it lies stranded and alive on the beach at Carlyon Bay, Cornwall on 13 August 2012 Getty Tragic photos show beached whales The lower jaw of a dead sperm whale that stranded itself on a beach in Hunstanton, Norfolk on 5 February 2016 Getty Tragic photos show beached whales One of the five sperm whales that were found washed ashore on beaches near Skegness, Lincolnshire over the weekend on 25 January 2016 Getty Tragic photos show beached whales Employees at work to skin the remains of a beached 60ft whale on 25 January 2013 AFP/Getty Tragic photos show beached whales Two long-finned pilot whales are stranded on a beach in the northern French city of Calais on 2 November 2015 AFP/Getty Tragic photos show beached whales A sperm whale lies dead after becoming stranded on a beach in Hunstanton, Norfolk on 5 February 2016 Getty Tragic photos show beached whales Crowds gather as a sperm whale lies dead after becoming stranded on a beach in Hunstanton, Norfolk on 5 February 2016 Getty

Mr Hesten was accompanied by staff from the directorate and wore a survival suit before leaping into the icy waters near the island of Rolfsoya to try and undo the harness.

“When I was in the water, it came really close ... and I managed to reach and unfasten the front buckle,” he told NRK.

The second strap was harder to remove, but Mr Hesten eventually managed to attach a hook to it, and as the whale swam off the harness was pulled free.

The fishers recovered the harness, which had the words “Equipment of St Petersburg” labelled on it.

“This is not something any Norwegian scientist has been doing. What we think is that this may come from Russia,” said Audun Rikardsen, professor at the Department of Arctic and Marine Biology at the University of Tromso.

“If this whale has this on for a long time, then it is not good for it,” he said.

“We know that in Russia they have had domestic whales in captivity and also that some of these have apparently been released. Then they often seek out boats.”

Mr Rikardsen contacted Russian researchers who told him the beluga had nothing to do with them.

“They tell me that most likely is the Russian navy in Murmansk,” he said.

One of his colleagues in the same field agreed. “If this comes from Russia, and there is great reason to believe it, then it is not Russian scientists, but rather the navy that has done this,” said Martin Biuw of the Institute of Marine Research.

They believe the harness could be used to attach cameras or other instruments.

Both the US and Russia trained marine mammals including whales, dolphins, sea lions and seals during the Cold War, Vietnam War and the Iraq War.

In the US the Navy Marine Mammal Programme is ongoing and is based in San Diego, California. Animals are trained to detect enemy sea mines, to protect ports and to recover objects from the sea bed.