NEW YORK • Four people were injured in a blast that rocked a subway station in the heart of Manhattan, in what New York's mayor said was an "attempted terrorist attack".

The blast - which took place at about 7am yesterday (8pm Singapore time) in the station at the Port Authority bus terminal, not far from New York's iconic Times Square - sparked commuter panic and travel disruptions.

The attack was the second on New Yorkers in six weeks, coming after a man in a rented truck drove up a crowded bike path on Halloween, killing eight and injuring 12.

It came at the height of the Christmas season, when the city is filled with daytrippers and tourists expecting a fairytale Manhattan.

The 27-year-old suspect, Akayed Ullah, was described as an immigrant from Bangladesh, officials said. He had strapped to his body the device that went off shortly after 7am, Police Commissioner James O'Neill said at a news conference near the scene. Ullah suffered serious burns but was expected to survive, officials said. Other victims had minor injuries.

"This was an attempted terrorist attack," Mayor Bill de Blasio told reporters. "Thank God the perpetrator did not achieve his ultimate goals."

New York Governor Andrew Cuomo said: "This is New York. The reality is that we are a target by many who would like to make a statement against democracy, against freedom."

The blast took place in an underground passageway at the Port Authority subway station, the authorities said. The suspect was walking eastbound in the passageway at the time. He was carrying a homemade explosive device, officials said. The weapon was based on a pipe bomb and was fixed to the suspect with zip ties and velcro, according to police.

Investigators are trying to determine if the device may have detonated prematurely, or partially, when it exploded.

"There was a stampede up the stairs to get out," said Mr Diego Fernandez, one of the commuters at Port Authority. "Everybody was scared and running and shouting."

Photos were circulating on social media of the suspect on the ground with his hands cuffed behind his back and injuries to his torso.

Former New York police chief Bill Bratton told MSNBC television that the suspect may have been acting in the name of the Islamic State in Iraq and Syria group.

President Donald Trump was briefed on the explosion, White House spokesman Sarah Huckabee Sanders wrote on Twitter.

New York is on high alert ahead of the holidays, which culminate every year with the giant New Year's Eve celebration in Times Square, attended by hundreds of thousands of revellers.

AGENCE FRANCE-PRESSE, BLOOMBERG, WASHINGTON POST