New York - A 73-year-old birdwatcher says she was raped on Wednesday in Central Park, possibly by a man angered because she photographed him exposing himself there.

The woman told investigators that the man asked “Do you remember me?” before attacking her at about 11am near the park's tranquil Strawberry Fields that serves as a memorial to John Lennon, Police Commissioner Raymond Kelly said at a news conference.

The woman, who regularly visits the park to watch birds, said she thinks the assailant was the same man she photographed masturbating about a week ago in another, more isolated part of the park, police said. She said he demanded she delete the image before they went their separate ways. Police said that initial encounter wasn't reported.

On Wednesday, investigators spoke to Eric Ozawa, a college professor and birdwatcher who had called the police, while other officers and detectives swarmed the scene in search of the suspect.

Ozawa, 34, told reporters he was in the park at about 11.30am when he noticed a pair of legs sticking out along the path but thought it was somebody sleeping. As Ozawa got closer, he realised it was a woman lying face down. Her face was badly swollen, she had a black eye and was covered in mulch, he said.

Still, she appeared “self-possessed and lucid”, he said.

The woman told Ozawa she had been mugged and raped, he said. He immediately called the police.

“It's shocking that it could happen in the park in broad daylight,” he said. “That someone could rape somebody in her 70s.”

Police blocked off much of the area near West 72nd Street and Central Park West as they hunted for a suspect described as a man in his 40s.

Emily Loubaton, 29, of Brooklyn, was in the park on a scavenger hunt that her company had organised.

“I think this is pretty disgusting, and so shocking it would happen on such a beautiful day in such a beautiful park,” she said.

Asked if she felt less safe in Central Park, she said: “I'd like to believe that New York City has turned the corner for the better. I mean, this isn't the 70s. But it definitely makes you pause before you walk in.”

Strawberry Fields was named after one of the Beatles' best-known songs, Strawberry Fields Forever. It was officially dedicated in 1985, five years after Mark David Chapman fired five shots outside the Dakota apartment house on December 8, 1980, killing Lennon. - Sapa-AP