The doctor told police the reason he built the sound-proofed bunker was because "he wanted to have a girlfriend," Stockholm chief prosecutor Peter Claeson told CNN.
Horrific details about the 38-year-old doctor's alleged crimes last September have drawn comparisons in the media to Josef Fritzl, an Austrian rapist and kidnapper who kept his daughter captive in a cellar for 24 years
Claeson said the man, who was charged January 11, admitted drugging, kidnapping and depriving the victim of liberty, but denied raping her.
The doctor's lawyer, Mari Schaub, told CNN her client denied the rape allegation and denied "the degree of deprivation of liberty charge" leveled against him.
While he admitted building the bunker, he had no intention of holding multiple people there over an extended period of time, as was alleged, and had no intention of sexually harming the victim, she said.
"He is a man who was mentally depressed and when at the police station, complied with all the requests of the police," she said.
"He is very much in regret of what he has done."
Claeson said the woman's ordeal began when the doctor drugged her in her apartment by serving her chocolate-dipped strawberries and orange juice that had been spiked with Rohypnol, a potent sedative known as a date-rape drug.
The woman was allegedly raped at the apartment, the prosecutor said.
Once she was unconscious, the doctor put her in a wheelchair and wheeled her to his car. He drove her about six hours to his home outside the city of Kristianstad in southern Sweden, where he had built the bunker, Claeson said.
The prosecutor said the structure -- which was self-contained, with its own plumbing and water supply -- was designed to hold more than one captive.
Claeson said the accused took medical samples from the victim and created a false identity under which the samples could be screened for sexual diseases. He told police he did this so he could have unprotected sex with the victim, Claeson said.
The woman was allegedly held for six days, and only escaped through an unlikely series of events. Once the man realized police were looking for the victim, he drove with her to a police station, armed with a gun, to tell officers that they were a couple, the prosecutor said.
But police asked to speak to the woman in private, and she told them of her ordeal, Claeson said.
The doctor had worked in several hospitals in the region, Claeson said.
His trial is due to begin in Stockholm on January 25.