A machete-wielding suspect arbitrarily attacked three people at New York City's Grand Central station before he was fatally shot by police.

The suspect slashed an 84-year-old man and a 65-year-old man about the head and face, and left a 70-year-old woman with cuts to her shoulder on a subway platform.

Police said the assailant, identified as 44-year-old Anthony Griffin, ignored repeated demands to drop the weapon and called himself Lucifer.

Authorities said no connection to terrorism was suspected in the incident, which led to trains being diverted at the biggest rail hub in the US.

New York Governor Kathy Hochul said in a statement that "innocent people were attacked in a senseless act of violence".

New York Mayor Zohran Mamdani praised officers for their rapid response and said police body camera footage of the incident would be released.

NYPD Police Commissioner Jessica Tisch told a news conference the suspect had entered the subway system on Saturday morning at Vernon Boulevard-Jackson Avenue in the borough of Queens.

He boarded the 7 train to Grand Central-42 Street station, where he slashed one person on the platform. The assailant moved upstairs to another platform where he slashed two other people.

One, the 84-year-old man, suffered significant lacerations to the head and face, while the 65-year-old man sustained similar injuries, as well as an open skull fracture, said Tisch.

Two transit officers in the vicinity were alerted at 09:40 local time (13:40 GMT).

"The individual was armed with a large knife, described as a machete, and was behaving erratically, repeatedly stating that he was Lucifer," said Tisch.

She said the assailant had ignored at least 20 demands to drop the weapon and "advanced towards the officers with the knife extended".

One officer shot the suspect twice before both attempted life-saving measures. But the suspect was later pronounced dead at Bellevue Hospital.

All three victims were taken to hospital with injuries that were not believed to be life-threatening. New York police urged residents to avoid the area due to the investigation.

The assailant had three prior arrests, but no Emotionally Disturbed Person (EDP) report history with the NYPD, said Tisch.