Law enforcement officials say they've linked a wanted man -- now dubbed the "Nor Cal Rapist" -- to assaults on 10 women in six counties since 1991.

Authorities said Friday that a multiagency task force is trying to assemble a detailed profile of the rapist who studies and stalks victims who live alone or with another woman.

During ordeals that last hours, he often blindfolds and binds victims with duct tape and chats with and apologizes to them, sometimes calling them afterward to say he was sorry for using their ATM cards, police said.

The assailant, who displays a gun or tells victims he is armed, has struck in Rohnert Park, Vallejo, Martinez, Woodland, Davis, Chico and Sacramento. He has been linked to the cases either through DNA or the similarities in the attacks, but so far investigators haven't matched the man's DNA sample with those on file in any database, authorities said.

The assailant is described as a white man in his late 30s or early 40s, 5-foot-8 to 5-foot-10, between 250 and 300 pounds, with brown spiked hair and a protruding belly.

He is believed to be driving a white 2001 to 2003 Toyota 4-Runner with tinted rear windows, a roof rack and moon roof, based on surveillance-camera footage from a neighbor of two victims in Sacramento last month, the first reported attacks since 2000.

Police throughout Northern California, the FBI and the state Department of Justice are working on the profile of the rapist, said Sacramento police Officer Michelle Lazark, a department spokeswoman.

Police noted that the first two victims were white but that he has since targeted Asian women. Authorities are intrigued by a gap in attacks after he raped a woman in Davis in 2000. He apparently didn't surface again until Oct. 13 this year, when he raped two women in Sacramento.

"We don't know whether the guy was in custody, if he got arrested, we just don't know," Lazark said. "We don't know if he moved out of state or if he was in the military. It's purely speculation."

Police said the rapist often recited personal details to the victims and, in the attacks last month in Sacramento, knew his way around the house where two victims lived, suggesting that he'd stalked or surveilled the women beforehand.

"He tracked her movements for some time, knew where she worked and knew some things about her that wouldn't just be spur of the moment," Lazark said. "We don't know if he saw these victims at their place of business and then followed them home, or if there's a link like they possibly go to the same gym or shop at the same supermarket."

Whatever the case, the attacker apparently has a fantasy of having a relationship with his victims, criminal profiler Brent Turvey said Friday.

"There's a duality here. This guy centers around the fantasy that they're willing participants," Turvey said. "This guy believes he knows them and thinks by spending time and watching them from afar, he's imagining in his mind an intimate relationship. But he's aware enough that if they can talk and move around and get away, they'll ruin it."

Turvey said the case evoked memories of a serial rapist in Louisiana who was a police officer investigating sex crimes. He wrote down license plate numbers belonging to women he found attractive and went to their homes, Turvey said.

The series of Northern California assaults began in 1991 when the man raped a woman in her Rohnert Park townhouse after getting through an unlocked sliding glass door, said Rohnert Park police Sgt. Joe Ferronato. The woman has since criticized police for failing to take her report seriously at the time, but Ferronato said the department is actively investigating the case.

The rapist then attacked a woman in Vallejo in 1992. In 1996, he wore a skeleton mask and attacked a woman in Martinez on Halloween and then called her at work less than three weeks afterward to apologize, Martinez Police Chief Dave Cutaia said.

Also in 1996, he tied up but didn't rape a Woodland woman. In 1997, he raped two women in Davis and a woman in Chico, and in 2000 he raped another woman in Davis, police said.