At centre, a view of the home of Norwegian billionaire Tom Hagen and his wife Anne-Elisabeth Falkevik Hagen in Fjellhamar. Norwegian police say her suspected kidnappers have demanded a ransom of 9-million euro (R144 million). Picture: Tore Meek/NTB scanpix via AP

Stockholm - The wife of one of Norway's wealthiest businessmen who has been missing since late October is feared to have been abducted, Norwegian media outlets reported on Wednesday.

A ransom of 9 million euros (roughly R144 million) has been demanded for Anne-Elisabeth Falkevik Hagen, who has been missing since October 31, according to Oslo daily VG.

Falkevik Hagen is married to Tom Hagen, an investor with business interests in power generation and real estate estimated to be worth 1.7 billion kroner (200 million dollars), according to financial site Kapital.

Police were due to give a press conference on the matter later Wednesday.

News of the disappearance was not made public previously due to a threatening note left at Falkevik Hagen's home in Akershus, near Oslo.

The ransom payment was requested in the cryptocurrency monero to make it harder to trace a transaction, dailies Aftenposten and VG reported.

A large police operation is underway. Norwegian police have also engaged international counterparts in Interpol and Europol as part of the probe.