Markku Ranta-Aho of Finland's National Bureau of Investigation told national YLE radio that the demand was addressed to the Finland-based company that owns the Arctic Sea, but would not give further details or say where the ship might be located.
There have been conflicting reports of the whereabouts of the vessel, with a Russian maritime website reporting that the ship's tracking system had suggested it was in the Bay of Biscay on Friday.
Other reports said it was believed to be more than 3,200km further south near Cape Verde.
"... the Somalis
do not have a monopoly on piracy or organised crime at sea"
Dmitry Rogozin, Moscow's ambassador to the Nato military alliance, has refused t give out details of the search for the vessel in order to protect the crew.
Nick Davis, a UK-based maritime expert, told Al Jazeera that if the ransom demand was bona fide it would "rattle the industry".
"For a vessel to be hijacked in European waters and be taken down to the west coast of Africa, this is a very technical hijacking, if it is, but is probably more extortion," he said.
"Certainly professionals are onboard that vessel for them to fully understand the requirements of shipping channels ... and the best time to turn off any sort of potential information service that could then lead the naval forces or police towards them."
Nothing has been heard of the Russian crew since the ship was reportedly boarded by armed and masked men in Swedish waters on July 24.
The vessel then went missing after passing through the English Channel on July 28.
It had been due to arrive in Algeria on August 4 with a cargo of Norwegian timber worth more than $1.42m.
Franz Lehr, a piracy expert at the University of St Andrews in Scotland, told Al Jazeera that it was unclear if the ransom demand was genuine or simply a hoax.
"It's all a very murky affair," he said. "My gut feeling is it's not typical organised piracy, it is something else, maybe there is a consignment of drugs or even weapons concealed on the ship."
The European Union has said that reported radio contacts with the ship were not consistent with usual patterns of piracy.
"Radio calls were apparently received from the ship which had supposedly been under attack twice, the first time off the Swedish coast then off the Portuguese coast," Martin Selmayr, a spokesman for the executive arm of the EU, said.
"From information currently available it would seem that these acts, such as they have been reported, have nothing in common with traditional acts of piracy or armed robbery at sea."
Pirate attacks in European waters are extremely rare, and the ship's disappearance on one of the world's main shipping routes has led to intense speculation over what may have occurred.
"It is good to highlight that the Somalis do not have a monopoly on piracy or organised crime at sea," Lehr told Al Jazeera.
"These things happen in other waters, like the South China Sea, the Straits of Malacca, the Caribbean, and now obviously in the Atlantic and North Sea."