Authorities are investigating an alleged manifesto posted online which purportedly claims responsibility for an "intentional" bomb which exploded in New York earlier today, injuring 29 people.

A manhunt for the person or persons responsible is underway and the city's governor has stated the attack was an act of terrorism but there are no connections to international terrorist groups. New York Police Department say they are currently vetting a Tumblr post claiming to be written by the person who planted a bomb.

The post titled “I Am The NY Bomber” has been taken down by Tumblr but sources within the police department told The New York Daily News that they are taking the page’s threats seriously and its content is subject to investigation.

CCTV captures moment of explosion in New York

“The explosives detonated in New York City, that was me,” the posting reads. “Those were just some tests, I know where I have made errors and I will not make the same mistake next time.”

“I did it because I cannot stand society. I cannot live in a world where homosexuals like myself as well as the rest of the LGBTQ+ community are looked down upon by society,” the author continues.

“I don’t know exactly how I feel about taking human lives. I suppose I’m just going to have to move forward knowing that what I am doing had a purpose and will in fact make a difference."

The authenticity of the posting has not been confirmed by authorities.

In pictures: New York bomb explosion Show all 25 1 /25 In pictures: New York bomb explosion In pictures: New York bomb explosion A police robot accidentally detonated one of five explosive devices left outside a train station in New Jersey. Officials said the bomb squad robot cut a wire on the mechanism in a bid to defuse it - but instead set off an explosion. The device had been left in a backpack and placed in a bin outside the train station in Elizabeth Universal News And Sport (Europe In pictures: New York bomb explosion A member of the New York City Police Department stands guard in Herald Square Getty Images In pictures: New York bomb explosion New York Mayor Bill de Blasio (3-R) and New York Governor Andrew Cuomo (2-R) tour the site of an explosion that occurred in the Chelsea neighborhood of New York Getty Images In pictures: New York bomb explosion New York Mayor Bill de Blasio and New York Governor Andrew Cuomo tour the site of an explosion that occurred in the Chelsea neighborhood of New York on September 18, 2016. The bomb that exploded in New York AFP/Getty In pictures: New York bomb explosion A genral view down the street near the site of an explosion that occurred in the Chelsea neighborhood of New York AFP/Getty Images In pictures: New York bomb explosion New York City Mayor Bill de Blasio (L) and New York Gov. Andrew Cuomo hug after touring the site of the bomb blast on 23rd St. in Manhattan's Chelsea neighborhood Getty Images In pictures: New York bomb explosion A mangled dumpster sits on the sidewalk at the site of an explosion that occurred in the Chelsea neighborhood of New York Getty Images In pictures: New York bomb explosion An explosion in a construction dumpster that injured 29 people is being labeled an "intentional act". A second device, a pressure cooker, was found four blocks away that an early investigation found was likely also a bomb Getty Images In pictures: New York bomb explosion New York Mayor Bill de Blasio (2-R) and New York Governor Andrew Cuomo (3-R) stand in front of a mangled dumpster while touring the site of an explosion that occurred in the Chelsea neighborhood of New York Getty Images In pictures: New York bomb explosion A member of the New York City Police Department K-9 Unit patrols on a subway train between Grand Central Terminal and Times Square Getty Images In pictures: New York bomb explosion FBI agents review the crime scene of remnants of bomb debris on 23rd St. in Manhattan's Chelsea neighborhood Getty Images In pictures: New York bomb explosion Members of the NYPD, FBI, ATF and other agencies investigate the the scene, following a late night explosion on West 23rd Street in New York AFP/Getty Images In pictures: New York bomb explosion Federal Bureau of Investigation (FBI) officials mark the ground near the site of an explosion in the Chelsea neighborhood REUTERS In pictures: New York bomb explosion New York Gov. Andrew Cuomo, right, walks from the scene of an explosion on West 23rd street in Manhattan AP In pictures: New York bomb explosion New York City Police Department (NYPD) officers stand near the site of an explosion REUTERS In pictures: New York bomb explosion Evidence markers on the street surround police and Federal Bureau of Investigation (FBI) officials near the site REUTERS In pictures: New York bomb explosion A fire truck is seen near a blocked off road near the site of an alleged bomb explosion on West 23rd Street AFP/Getty Images In pictures: New York bomb explosion New York City firefighters stand near the site of the explosion in the Chelsea neighborhood REUTERS In pictures: New York bomb explosion A New York City Police emergency services officer and his dog check a bin close to the scene EPA In pictures: New York bomb explosion New York City Police and Fire Department at the scene of the explosion EPA In pictures: New York bomb explosion A New York City firefighter uses a wheeled stretcher to carry supplies near the site of the explosion REUTERS In pictures: New York bomb explosion A New York City Police emergency service heavy weapons officer guards close to the scene of the explosion on 23rd Street between 6th and 7th Avenue EPA In pictures: New York bomb explosion New York Mayor Bill de Blasio, center, and NYPD Chief of Department James O'Neill, center right, speak during a press conference near the scene AP In pictures: New York bomb explosion New York City Police Emergency Services units are deployed on 27th Street and 7th Avenue where police found a second explosive device EPA In pictures: New York bomb explosion Police investigators look through the debris on the street in front of St. Vincent de Paul church where the explosion occurred EPA

The bomb exploded in the Chelsea area of New York City, a neighourhood characterised by its art galleries and nightlife.

Officials found what they determined to be another explosive device just four blocks away from the blast late Saturday night.

Speaking at the scene, New York City governor Andrew Cuomo said: “We really were very lucky that there were no fatalities at the time", adding that all 29 people who were injured have been released from the hospital. Many of the injuries were caused by shrapnel from the explosion. Witnesses said the impact came from inside a dumpster near the Avenue of Americas.

Now, more than 1,000 additional state police officers and national guard officials will patrol the city's bus and subway stations after the blast on Saturday night, Cuomo announced at Sunday’s press conference. He encouraged New Yorkers to go about their business as normal and reassured them that the city is once again safe.

“We're not going to let them win,” Mr Cuomo said at the scene. “We're not going to let them instill fear.”

The powerful bang was reported hours after an explosion let out in Seaside Park, New Jersey. Officials said a charity race—the Seaside Semper Five event for members of the US Marine Corps— was scheduled to pass through but thanks to an unexpected delay, no one was injured.