NEW YORK (Reuters) - A New York City subway train struck and killed a 58-year-old man who was pushed onto the track by another man who escaped and is still at large, police said.

The attacker, who appeared to be in his 20s, pushed the older man onto the track as the southbound train on the N-Q-R line was pulling into the station at 49th Street near Times Square, a police spokesman said.

Police declined to comment on what may have led to the crime.

Witnesses saw the younger man talking to himself, leading to suspicion he may have been mentally disturbed, police said.

"You almost heard a thud. I wasn't sure if it had anything to do with the man being struck," said one unidentified witness. "That's when I heard people yelling, people running out."

The victim was trapped between the train and the platform, and a doctor who happened to be in the station pronounced him dead, NY1 television reported.

(Reporting by Daniel Trotta; editing by Christopher Wilson)