Witnesses in New York have described hearing an "extremely loud noise" and "everything shaking" when an explosion struck Manhattan, New York, injuring 29 people.

Following the explosion, which New York Mayor Bill de Blasio has described as an "intentional act" but not terror-related, a suspicious device discovered a few blocks away was removed by authorities.

Tsi Tsi Mallett was driving down 23rd street when the explosion took place.

Mr Mallett said: "It was really loud, it hurt my eardrums. My 10-year-old boy was sat in the back seat of the car, and the explosion blew the back window out."

Mayor Bill de Blasio, center, and NYPD Chief of Department James O'Neill, center right, speak during a press conference near the scene (AP)

Chris Gonzalez, from Dallas, was having dinner with friends in the Chelsea area at the time.

The 26-year-old said: "We felt it, we heard it, the restaurant went real quiet. It wasn't like jolting or anything, everyone just went quiet."

Police investigators look through the debris on the street in front of St. Vincent de Paul church where the explosion occurred (EPA)

Emily Brookstein, 30, told Mailonline:"I was eating at the restaurant Mira with my family and we heard a huge noise and the entire restaurant shook.

"My dad thought it was a thunder but we obviously realized later that wasn't the case.

"We came out of the restaurant and could see smoke. Some say it was a subway bomb, but it was definitely an explosion."

A New York City firefighter uses a wheeled stretcher to carry supplies near the site of the explosion (Reuters)

Rudy Alcide, a bouncer at Vanity Nightclub at 21st Street and 6th Avenue, had first thought something large had fallen.

He said:"It was an extremely loud noise, everything was shaking, the windows were shaking, it was crazy.

"It was extremely loud, almost like thunder, but louder."

Simitrio Ramirez, 53, who lives nearby in the area said he felt the explosion while at home. He added:"With construction in the area, I thought something big fell."

A New York City Police emergency services officer and his dog check a bin close to the scene (EPA)

The blast happened on West 23rd street, in front of a residence for the blind, near a major thoroughfare with many restaurants and a Trader Joe's supermarket.

Witnesses say the explosion at about 8:30 p.m. blew out the windows of businesses and scattered debris in the area. Officials said no evacuations were necessary.

A law enforcement official told AP the second device that officers investigated four blocks from the scene seemed to be a pressure cooker attached by wiring to a mobile phone.

New York City Police Emergency Services units were deployed on 27th Street and 7th Avenue where police found a second explosive device (EPA)

The source, speaking anonymously, said the device was found inside a plastic bag on West 27th Street.

The device was removed with a robot and taken to the department firing range in the Bronx, officials said.

A New York City Police emergency service heavy weapons officer guards close to the scene of an explosion on 23rd Street between 6th and 7th Avenue (EPA)

Fire Commissioner Daniel Nigro said several people were taken to hospitals with injuries.

One of the injured suffered a puncture wound that was considered serious.

Mr Nigro explained the other injuries were minor, described as scrapes and bruises.

Emergency services responding to reported Manhattan blast (Reuters)

Mayor de Blasio told a press conference near the scene in Chelsea: "Tonight, New York City experienced a very bad incident. We have no credible and specific threat at this moment."