Just in: Suspect identified in New York bombing is US naturalised Afghani Ahmad Khan Rahami, 28, says New York mayor.

A powerful explosion struck a bustling upscale neighbourhood in New York injuring 29 people in what the mayor on Sunday described as an "intentional act" as police found a second explosive device nearby, a pressure cooker with wires, hours before world leaders descend in New York for the 71st United Nations General Assembly session.

The explosion -- which happened shortly after a pipe bomb went off in a garbage can in New Jersey -- occurred in Manhattan's Chelsea neighbourhood, a busy residential and commercial area frequented by tourists and city residents.

The impact damaged windows of nearby buildings and cars and sent crowds running from the scene. The blast seemed to shake the entire block, sending debris into the street. There were no immediate claim of responsibility for the blast that occurred at 8:30 pm local time on Saturday, a busy time of the weekend for over 8 million New Yorkers, who just marked the 15th anniversary of the September 2001 attacks.