NYC- A woman raped inside an upper East Side apartment last week is a call girl and cops believe the attack could be linked to a feud between rival sex rings, law enforcement sources said yesterday.

The 30-year-old Asian victim placed an ad in The Village Voice offering to give patrons a “full-body” massage, the sources said.

She then made a date with a man over the phone and agreed to give him a “rubdown” on Thursday in an apartment on E. 81st St. and York Ave., the sources said.

Two men arrived at the apartment about 1:30 a.m. and as the woman was talking to them through the door, a third man showed up and flashed a gun, the sources said.

The men then pushed their way into the apartment. Two of them raped the woman and the third sexually assaulted her, police said.

“It appears her attackers were trying to scare her and put her operation out of business,” a source said yesterday.

The attackers stole several hundred dollars in cash, an unknown amount of foreign currency and some high-end electronics, police said.

Neighbors and people who work on the block said as many as five Asian women, all Vietnamese, live in the apartment where the victim was raped.

“Many ladies live there, though no one sees many men coming in or out,” said doorman William Aguilar, 42, who works in a residential building across the street. “To get in, you would have to get past two locked doors.”

Aguilar said he believes he saw one of the three suspects lurking around the victim’s apartment building the day before the attack.

“When he saw me here, he walked away,” Aguilar said. “When I see a new face, I remember it. He looked suspicious.”