Norway farms around 570,000 tonnes of Atlantic salmon a year - the biggest global producer from a total of 1.25 million tonnes - and a scare could hit worldwide demand, while supply remains fairly inelastic, said Klaus Hatlebrekke, a market analyst with the Norwegian bank DnB NOR.

"If the Russian findings are correct, then worry will spread to Asia and the United States and Europe and really hurt global salmon demand," he said.

And the ban will already weaken prices as fish farms have to sell salmon when they reach a certain size or they will die and be worthless, he said.

This year the price of a kilo of salmon has bobbed between 23 and nearly 29 Norwegian crowns ($3.42 - $4.31), the highest since 2001.

Seafood is Norway's most valuable export after energy and metal and Russia the biggest and fastest growing seafood market.

NORWAY CONTESTS FINDINGS

Russia has imported 60 percent more Norwegian salmon so far this year than it did last year, and demand is expected to grow further as the middle class increases and logistics improve.

But last week Russian vets said they found levels of lead 18 times higher than safety levels and cadmium 3.5 times higher.

Norway refutes the findings and says that there must be a mistake as such levels are almost unbelievably high.

Salmon farmers have had to fight off scares before, and this scare would also blow over, Hatlebrekke said.

"There has to be some mistake. The levels are so huge that the fish would be dead in the water," he said.

Norway has shown the Russian agriculture ministry its own findings that levels of lead and cadmium at the four farming firms are within the legal barrier and has invited Russian vets over to inspect the farms for themselves, Ingellis Jacobsen, Norway's seafood marketing manager in Russia, told Reuters from the Norwegian embassy in Moscow.

"It's important to get the Russian vets to Norway to show them the farms are not infected," she said.