A man has died after he was put into a chokehold during a confrontation on a New York City subway train.

Jordan Neely’s death was ruled a homicide by the city’s medical examiner on Wednesday, who said he died from compression of the neck.

The homeless 30-year-old Michael Jackson impersonator had been yelling he was hungry and ready to die on a train in Manhattan, witnesses and police said, when he was restrained by at least three other passengers.

The incident, which happened at around 2.27pm on Monday, was filmed by a freelance journalist and posted online.

It showed a man lying beneath Mr Neely – a veteran Marine – holding him in a headlock position for several minutes as he tried and failed to break free.

A second passenger pinned Mr Neely’s arms, while a third person held down his shoulder.

Mr Neely was found unconscious by police after the train stopped and he was taken to hospital where he was pronounced dead.

The 24-year-old veteran was taken into police custody for questioning and released without charges.

"As part of our rigorous ongoing investigation, we will review the medical examiner’s report, assess all available video and photo footage, identify and interview as many witnesses as possible, and obtain additional medical records," Doug Cohen, a spokesman for Manhattan district attorney’s office, said.

Juan Alberto Vazquez, the journalist who filmed the altercation, told the New York Post that Mr Neely was screaming "in an aggressive manner" and complaining of hunger and thirst.

Mr Neely did not physically attack anyone, he said, adding the veteran approached the man after he threw his jacket to the ground.

Protests have been held on the subway and on the streets of Manhattan following Mr Neely’s death, with demonstrators calling for an arrest.

Dave Giffen, the executive director at Coalition for the Homeless, blamed city and state officials for an inadequate response to the mental health crisis – and questioned why the veteran was not facing criminal charges.

"The fact that someone who took the life of a distressed, mentally ill human being on a subway could be set free without facing any consequences is shocking," he said.

"This is an absolute travesty that must be investigated immediately."

Mr Neely’s father, Andre Zachery, told the New York Daily News he had not seen his son in four years.

He said Mr Neely’s mother also died violently. Christie Neely was strangled in New Jersey in 2007, according to news reports at the time. Her body was found days later in a suitcase on a street.

Mr Neely, who was 14 when she died, gave evidence against his mother’s boyfriend at his murder trial.

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