Witnesses have described terrifying scenes with people "running for their lives" after a terror-related explosion inside the New York subway system during Monday morning rush hour.
Police have named the suspect as Akayed Ullah, 27, who strapped a pipe bomb to himself with a combination of velcro and zip ties that exploded in the Port Authority Bus Terminal station about 7.20am.
New York governor Andrew Cuomo described the explosive as a "low-tech device".
The New York Police Department confirmed Mr Ullah was in custody at Bellevue Hospital in a serious condition suffering from burns to his hands and abdomen.
Local media reported that the suspect was from Bangladesh and lived in Brooklyn, having been in the US for seven years.
Three other people suffered "non-life-threatening" injuries including ringing in their ears consistent with being close to an explosion, the New York Fire Department confirmed. One of the injured was a Port Authority police officer.
The device went off in an underground passageway between 7th and 8th avenues on 42nd St and was captured on surveillance video.
New York mayor Bill de Blasio called it an "attempted terrorist attack" and said there were "no known additional incidents or activities".
"The choice of New York is always for a reason because we're a beacon to the world and we actually show we show that a society of many faiths and many backgrounds can work and we show that democracy can work" he said. "Our enemies want to undermine that."
Witness Hakeem Blay, who works for New York sightseeing bus company TopView, told news.com.au he was standing outside the station when he heard a loud "boom" and saw people running from the station.
"In the first minute or three minutes I just saw people coming out of the building, running out. I'm like what's going on?" he said.
"I felt like something is going wrong because I've never heard that explosion before."
"I just didn't know what is going on; they were running for their lives. Very scary."
Commuter Diego Fernandez, who was caught up in the chaos, said: "There was a stampede up the stairs to get out … Everybody was scared and running and shouting."
Witness Alicja Wlodkowski, 51, told The New York Times she was in a restaurant when she saw people running.
"A woman fell, and nobody even stopped to help her because it was so crazy," she said. "Then it all slowed down. I was standing and watching and scared."
The Port Authority Bus Terminal has now reopened and trains throughout the city are back up and running, after authorities completed a sweep of the scene.
"This is New York. The reality is we are a target for many who would like to make a statement against democracy, against freedom," Mr Cuomo said at a press conference.
"We have the Statue of Liberty in our harbour and that makes us an international target; we understand that … (but) this is New York and we call pitch together and we are a savvy people and we keep our eyes open … and we have the best law enforcement on the globe."
The large bus and train station is one of the busiest in New York and connects Manhattan to New Jersey and other states. It is located directly opposite The New York Times office and is just blocks from Times Square in the heart of Midtown.
Police closed off the busy 8th Ave surrounding the station within minutes and footage from the scene showed an orderly evacuation.
Earlier, police confirmed they were investigating an explosion of "unknown origin" in
Manhattan, and that people were being evacuated from several train lines.
"The NYPD is responding to reports of an explosion of unknown origin at 42nd Street and 8th Ave, #Manhattan. The A, C and E line are being evacuated at this time. Info is preliminary, more when available," the New York Police Department tweeted.
White House press secretary Sarah Sanders said US President Donald Trump had been briefed on the explosion.
However the President's first tweet of the morning was not related to the unfolding situation in his home city, but to lambaste The New York Times for its news coverage.
"Another false story, this time in the Failing @nytimes, that I watch 4-8 hours of television a day — Wrong!" he wrote.
"Also, I seldom, if ever, watch CNN or MSNBC, both of which I consider Fake News. I never watch Don Lemon, who I once called the 'dumbest man on television!' Bad Reporting."
The event comes after eight people were killed and 11 injured after a 29-year-old man drove a white truck down a cycle lane into people on Halloween.
Sayfullo Saipov pleaded not guilty to murder and other criminal charges.