NEW YORK (AP) _ An unidentified woman savagely beaten in Central Park was spotted having an angry confrontation with a young man at about the time of the attack, police said Wednesday.

Police received several tips and anonymous phone calls reporting the Tuesday afternoon argument, said Deputy Inspector Wayne Bax.

``We feel there are a number of witnesses out there who can not only identify the victim, but describe what happened,'' Bax said during a news conference. ``We believe there was a confrontation which may have drawn people's attention.''

One investigator, speaking on condition of anonymity, said police were preparing a sketch of the assailant and believe that the assailant knew the victim.

Investigators found ``indication of a sexual attack,'' but the victim was not raped, Police Commissioner Howard Safir said. Safir said a team of 50 detectives will work on the case until all leads are exhausted.

``And right now there are many leads,'' he said.

Mayor Rudolph Giuliani also announced an $11,000 reward for information leading to the arrest and conviction of the assailant.

A passerby found the woman bleeding from the ears and unconscious shortly after 4 p.m. on a pathway about 100 feet inside the park at 82nd Street. She was steps away from a park playground and not far from the high-priced apartment buildings of the city's Upper West Side.

The woman who found the victim on Tuesday, Iris Fass, told The New York Times that the victim's skirt was pulled down below her hips and her tank top and bra were yanked down.

Fass, a professional dog walker, told the Times on Wednesday that the victim was having abdominal spasms and her hands were moving slightly, but she was unresponsive. ``It was horrible,'' she said.

The woman was in critical condition Wednesday with severe head injuries that police believe were caused by a blunt object. No weapon was found.

Police and park rangers searched the park for evidence through Tuesday night and into Wednesday afternoon, even removing a section of the paved path with a forklift. But the investigation was stymied by the absence of a key piece of information: the victim's name.

Despite wide distribution of a sketch of the dark-haired young woman _ made as she lay in an intensive care ward _ no one had come forward to identify her.

The 5-foot-2, 110-pound woman, who is in her 20s, appeared too well-groomed to be homeless, police said. She was dressed in a red tank top, a black-and-white checked knee-length skirt and New Balance sneakers.

Asked whether she might have been from out of town, Bax would only say that police believe she was ``someone who knew the area.''

City officials labeled the attack ``an aberration,'' noting that reports of crime in the park have fallen more than 60 percent in the past three years.

But the incident revived memories of similar, high-profile attacks on women in a park New Yorkers have always seen as a peaceful refuge from city streets.

Last fall, a jogger was murdered in the park's northern end, not far from where another runner was raped and beaten by a teen-age gang in 1989. Both of those women were attacked when the park was more deserted, one at night and the other in the early dawn.

On Wednesday morning, just outside the cordoned-off crime scene, joggers, dog-walkers and mothers with strollers stuck to routine.

``It's nothing new, these attacks in the park,'' said Alberto Arroyo, 80, a longtime park-goer.

``This park is a secure place, but you have to use common sense. When it's empty, don't go in. When there are a lot of people around, it's safe.''