A 28-year-old naturalized US citizen from Afghanistan was being sought Monday for questioning in connection with a weekend explosion in New York City, the FBI said.
The suspect was identified as Afghan-born Ahmad Khan Rahami, 28, whose last known address was in the town of Elizabeth, New Jersey, just outside New York City.
Police discovered several explosive devices late Sunday in a suspicious package at a train station in Elizabeth. One of the devices blew up early Monday as bomb experts were working to defuse it, the FBI's Newark bureau tweeted, confirming that there were no injuries in the unintentional detonation.
Police in New York and neighbouring New Jersey have been on alert in the wake of bomb blasts Saturday, first along the planned route of a US Marines-sponsored charity run in New Jersey, and later in New York City's fashionable Chelsea neighbourhood.
No one was injured in the New Jersey explosion, while the Chelsea blast injured 29 people and was soon followed by the discovery of a second device blocks away in Manhattan.
The Chelsea bomb appeared to have been built from a pressure cooker, much like the unexploded device found nearby.
The incidents have prompted New York state officials to tighten security, just as the annual UN General Assembly debates ramp up this week.
The Chelsea blast struck 3 kilometres from UN headquarters on the East River.
New York Mayor Bill de Blasio on Sunday vowed a "bigger than ever" police presence to protect the United Nations.
The US Homeland Security Department was "actively monitoring and participating in the investigations" of both the New York and New Jersey explosions, Homeland Security Secretary Jeh Johnson said.
He noted that the UN General Assembly debate, which begins Tuesday, was already designated a national special security event, for which thousands of federal personnel led by the Secret Service were deploying to the city.
"Any area in New York City associated with [the UN General Assembly] will therefore be subject to an extraordinarily high level of surveillance and security," Johnson said.
US President Barack Obama was to meet Monday with Chinese Premier Li Keqiang and later Iraqi Prime Minister Haider al-Abadi at the Lotte New York Palace Hotel.
Obama was to visit the US mission outside the United Nations and spend the night in the city, before co-hosting a Tuesday summit on the global refugee crisis.
New York Governor Andrew Cuomo ordered 1,000 additional police officers and National Guard members to patrol New York streets after the Chelsea bombing, which authorities have so far not tied to international terrorism.
"We will find whoever did this or whatever group did this, and they will be brought to justice, period," Cuomo said.
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