An undated police handout shows Norwegian Anne-Elisabeth Falkevik Hagen, who is the wife of real estate investor Tom Hagen, and has been kidnapped according to police in Norway. NTB SCANPIX/REUTERS

Copenhagen, Denmark -- Norway's police said Wednesday the missing wife of one of Norway's richest men has been abducted, and that her suspected kidnappers have demanded a ransom.

Chief investigator Tommy Broeske said 68-year-old Anne-Elisabeth Falkevik Hagen has been missing since Oct. 31. Her husband Tom Hagen -- a real estate investor and owner of power facilities -- is number 172 on a list of the country's 400 most wealthy people published by Norway's financial magazine Kapital. His fortune in 2018 amounted to nearly 1.7 billion kroner ($2 billion), according to Norwegian news agency NTB.

Police said a note found in the couple's house, east of Oslo, described what would happen to her if the demanded ransom wasn't paid in the cryptocurrency Monero.

Get Breaking News Delivered to Your Inbox

Police did not give a figure for the ransom amount, but Norway's VG newspaper reported it was 9 million euros ($10.3 million.)

The newspaper reported that the note said Falkevik Hagen would be killed if police were involved. Broeske declined to comment other than saying "the threats (in the note) were of a very serious character."

"The reason for us to go public with this case now is that despite a broad and extensive investigation, we need more information," he told a news conference.

The house (C) of Norwegian real estate investor Tom Hagen and his wife Anne-Elisabeth Falkevik Hagen, who according to the authorities is suspected to have been kidnapped, in Fjellhamar, Norway, Jan. 9, 2019. NTB SCANPIX/REUTERS

"We have no suspects in this case," he said. Police have been "on the case for several weeks. That is all I'd say," he added.

Broeske said "those behind have chosen to communicate digitally and we have had no other type of contact." Police had urged the family not to pay any ransom.

Police believe she disappeared from the couple's home, some 31 miles from the Swedish border. Broeske said they were working with Europol and Interpol on the case.