Oslo, Jan 9 (IANS): The wife of a Norwegian multi-millionaire businessman has been missing for months after being abducted and the kidnappers have demanded a ransom to be paid in cryptocurrency, the police said on Wednesday.

Anne-Elisabeth Falkevik Hagen, 68, married to Tom Hagen -- a businessman with an estimated fortune of 1.7 billion Norwegian krone (($199 million) made in the real estate and energy industries -- disappeared from her home near Oslo on October 31, the BBC reported.

The investigation had been continuing since then, the police said, but was given "a low profile" because "very serious threats had been made".

According to the police, someone claiming to be the kidnapper demanded a ransom to be paid in the cryptocurrency Monero, a digital currency similar to Bitcoin. The Norwegian media said that the kidnappers demanded a ransom of 9 million euros ($10 million).

"The main hypothesis has always been that the woman was abducted against her will," Inspector Tommy Brøske said in a statement cited by Efe news. "During this time we have not received any signs of life of the missing person nor that she is no longer alive," he added.

"Extensive forensic investigations have been carried out at the address, and several tracks have been found in the house," the statement said.

Hagen's home is near the Langvannet hiking area and the police had asked anybody who was walking around the neighbourhood on the morning she went missing to come forward whether they saw something suspicious.