US authorities were searching on Monday for an Afghanistan-born American in connection with a New York City bombing that left dozens injured and could be linked to pipe bombs found in New Jersey.

Investigators believe more people were involved in the New York and New Jersey bombing plots, two US officials told Reuters.

The New York Police Department released a photo of 28-year-old Ahmad Khan Rahami of Elizabeth, New Jersey, to question him about a Saturday night explosion that injured 29 people in Manhattan's Chelsea neighborhood and for a blast earlier that day in Seaside Park, New Jersey, authorities said.

New York Mayor Bill de Blasio told CNN that Rahami might be armed and dangerous.

The attacks came as world leaders prepared to gather at the UN in New York for the annual General Assembly. The Chelsea bombing, coming just days after the 15th anniversary of the Sept 11 attacks on the US, put the most populous US city on edge.

"We're going to have more security personnel than ever assembled over this next week during the UN General Assembly," New York Governor Andrew Cuomo said on CNN.

"The evidence might suggest a foreign connection," Cuomo said in television interviews on Monday morning.

Federal authorities now believe that the explosion in Chelsea, where another explosive device was found nearby, was linked to as many as six explosive devices found just outside New York in Elizabeth, Homeland Security officials told Reuters.

No one was injured in the Saturday morning explosion along the route of a running race in Seaside Park, about 60 miles south of Manhattan, New Jersey State Police said.

White House spokesman Josh Earnest said in television interviews that President Barack Obama, who is already in New York, was being briefed on the case.

The two US presidential candidates weighed in on the New York bombing.

"I think this is something that maybe will ... happen more and more all over the country," Republican nominee Donald Trump said in an interview with Fox News on Monday.

Democratic nominee Hillary Clinton said on Monday: "The threat is real, but so is our resolve."

In a news conference, she said the US needed to work with its allies to combat global terrorism and that the country should launch an "intelligence surge" to detect attacks before they are carried out.

SEARCHING NEW JERSEY HOME

A Federal Bureau of Investigation poster says Rahami was a resident of Elizabeth, where agents were executing a search warrant on Monday morning after explosive devices were found at a train station in that city, Mayor Christian Bollwage told CNN.

Rahami was not listed on US counterterrorism databases, several US officials said. A group of men were stopped and questioned in Brooklyn, New York, on Sunday night in connection with the explosions, but their current status was unclear, other national security sources said.

Cuomo said that, while the bombs discovered in Manhattan and New Jersey were not identical, there were "certain commonalities" among the chemicals and technologies used.

The raid in Elizabeth came hours after an explosive device left near a train station there blew up when a bomb squad robot cut a wire on the mechanism, the mayor said. It was one of as many as five potential bombs found at the site.

No one was injured in the blast from the device, which had been left in a backpack placed in a trash can near the station and a bar, Bollwage told reporters earlier.

As many as five potential explosive devices tumbled out of the backpack when it was emptied, Bollwage said. After cordoning off the area, a bomb squad used a robot to cut a wire to try to disable the device but inadvertently set off an explosion, he said.  - Reuters