In photos, Hilton has an obviously swollen lip and bruises up and down both arms.

She has said the bruising came in Los Angeles Monday evening, after she and Carter joined pal Amanda Demme at the Argyle Hotel, where Demme throws a weekly party.

"They were dirty dancing together," said one Argyle spy. "They were very lovey-dovey, staring into each other's eyes. We all thought they were back together."

But after Hilton and the ex-Backstreet Boy left the Argyle to party at another club, Joseph's, the mood turned sour.

"Nick wanted to leave, Paris didn't," said a Hilton pal, adding, "Nick forced Paris to leave, he made her get in a cab with him."

Hilton alleges to friends Carter later lost his temper.

Friends say Hilton is "scared to death."

The pal added: "He has major anger-management issues . . . We have seen bruises on her before and asked her about them. She has always denied it — until now."

Another Paris pal added, "Nick made his bed, now he has to lie in it."

A friend of her sister, Nicky Hilton, confirmed to yet another source that both Nicky and Paris claim the person responsible for Paris' bruises is Carter.

Hilton's rep, Tracy Shaffer, declined comment.

Carter's lawyer, Marty Singer, fiercely denied Carter had anything to do with the bruises on Hilton, claiming Hilton is spreading rumors because she's angry with the pop star.

"Even though they broke up, they spent Monday night together, and Paris left Nick's house Tuesday morning happy," Singer said. "This is all because Paris was upset by what Nick told People magazine."

Singer also claimed that Hilton had been scheduled for a photo shoot Tuesday with celebrity shutterbug David LaChapelle. "It was going to be an S&M shoot," the lawyer said.

Carter told his side of the breakup story to People, while Hilton told her side to a rival magazine, Us Weekly. Hilton gave no indication that violence contributed to the breakup.

Hilton said, "I need time alone," before revealing that she broke up with Carter in a phone call.

Hilton did say her friends weren't happy with her relationship.

"Nicole [Richie] will be happy. She didn't like me with Nick," Hilton said.

The magazine quoted a friend of Hilton saying: "Nick was very jealous of Paris and her career. He'd get mad at all the attention she got."

Singer fumed: "This is reciprocity. On Tuesday, he drove her to a business meeting and she called him later that night to see if he wanted to go out with her to some event. He said no! They had a big argument Thursday after People hit the newsstands because she was upset because he [had told the magazine] about her name tattooed on him. In our opinion, it's clearly retaliation."

When told of Singer's claims, Shaffer snapped, "No comment!"

Meanwhile, Hilton has tried to maintain her busy social schedule. On Wednesday, Hilton hit another L.A. club, Concorde, with sister Nicky and actors Lindsay Lohan and Wilmer Valderrama.

Hilton flew to New York yesterday to join her family in Southampton to attend a benefit for her recently deceased grandmother.