29 injured in 'intentional' explosion in NYC neighbourhood

A powerful explosion today rocked New York's upscale neighbourhood injuring 29 people, in what the mayor described was an "intentional act", hours before world leaders arrive here for the UN General Assembly session even as police also found a pressure cooker with wires nearby.

The explosion - which came hours after a pipe bomb went off in a garbage can in New Jersey - occurred in Manhattan's Chelsea neighbourhood at 23rd St. And 6th Avenue, a busy residential and commercial area frequented by tourists and city residents, around 8:30 pm (local time) yesterday.

President Barack Obama, who is set to visit the city for the UNGA session beginning tomorrow, has been apprised of the explosion, a White House official said.

New York City Mayor Bill de Blasio said the number of people injured is now 29 but none is life threatening except one who is in "serious" condition.

The Mayor described the explosion as an "intentional act" but said there is no evidence at this point of a terror link.

He said the city "experienced a very serious incident" and injuries are significant but added that there is "no evidence at this point of a terror connection" even as early indications suggest "this was an intentional act".

"There is no specific and credible threat at this time from any terror organisation", he said.

A second Manhattan site is under investigation, Blasio said while addressing a press conference at the scene.

Local officials said the device at a second location few blocks away in Chelsea appears to be a pressure cooker, with dark coloured wiring coming out of the top centre of the device. The device is connected by silver duct tape to a small device attached to the outside of the pressure cooker.

New York City new Police Commissioner James O Neill, who had his first day at the city's police chief yesterday, that the "exact cause of the explosion has not yet been determined" and personnel from the police department, FBI, bomb squad and counter-terrorism departments are on the scene.

The Police Commissioner added that a "second site" is being treated at 27th street between 6th and 7th avenues by the police but did not provide more details.

Police said investigations are ongoing and advised people to avoid the area.

As a "precautionary measure" residents living in the 27th street between 6th and 7th avenues to "stay away" from windows facing 27th street "until we clear the area of a suspicious package", they said, adding this is a precautionary measure only and they are not evacuating the area.

The Mayor also added that at this point there is "no specific connection" to the incident in New Jersey earlier in the day in which an explosion occurred in a garbage can.

"We are not going to let anyone change us, intimidate us," the mayor said.

Authorities said "extensive search" is being conducted in the area and the neighbourhood and ruled out gas as the reason for the explosion.

Security is already tight in the city as nearly 190 world leaders will arrive in the city for the about week-long annual UN General Assembly session.