Married to a businessman who made his fortune in real estate and the energy sector, 68-year-old Anne-Elisabeth Falkevik disappeared on October 31, the Verdens Gang (VG) newspaper said.
A ransom demand for nine million euros ($10.3 million) in cryptocurrency has been issued for her release, VG said.
The kidnappers have threatened to use violence against her if her family does not meet their demands, Norway’s newspaper of reference Aftenposten said, adding that there had been limited contact with the suspects.
Events like this are extremely rare in the wealthy Scandinavian country, which enjoys a generally low crime rate.
Norwegian police confirmed that “a woman in her late 60s is believed to have been kidnapped from her home in Lorenskog”, around 20 kilometers (12 miles) from Oslo, but did not disclose her identity.
Police were scheduled to hold a press conference later Wednesday.
The missing woman’s husband, Tom Hagen, 68, is Norway’s 172nd richest man, according to the magazine Kapital, with an estimated fortune of 1.7 billion kroner (174 million euros, $200 million).
A real estate investor, he owns 70 percent of electricity company Elkraft which he co-founded in 1992, Norwegian media reported.