United States President Barack Obama has urged Americans not to succumb to fear following two bomb explosions and a stabbing incident at the weekend.
"Even as we have to be vigilant and aggressive, both in preventing senseless acts of violence but also making sure that we find those who carry out such acts and bring them to justice, we all have a role to play as citizens in making sure that we don't succumb to that fear," he said.
He was speaking as police took a suspect into custody in connection with last Saturday night's explosion in the Chelsea neighbourhood in New York City.
Top officials say they do not rule out the possibility of a foreign connection. The suspect was identified as Ahmad Khan Rahami, a 28-year- old of Afghan descent.
Earlier, Democratic presidential nominee Hillary Clinton, speaking in White Plains, New York, also urged Americans to "be vigilant but not afraid".
"We choose resolve, not fear... we are stronger together in the face of this threat," she said, also noting the importance of building trust between law enforcement and Muslim American communities.
In contrast, her Republican rival Donald Trump called America "weak" and predicted there could be more attacks.
"Our country has been weak. We're letting people in by the thousands and tens of thousands. I've been saying, you've got to stop it," he told Fox.
On Sunday night in Elizabeth, New Jersey, five pipe bombs were found, one of which was accidentally detonated by a Federal Bureau of Investigation (FBI) robot.
This brings the number of explosions since the weekend to three. The two explosions last Saturday were in West 23rd Street in Chelsea, New York City, injuring 29 people, and in Seaside Park, New Jersey, where there were no injuries.
Homeland security officials told the Reuters news agency that the explosive devices in New York and New Jersey were linked.
The explosions came just after the 15th anniversary of the Sept 11 attacks and just two days before the United Nations General Assembly meeting, which will be attended by Mr Obama and other heads of state.
New York Mayor Bill de Blasio said yesterday morning: "In the coming hours, we are going to be able to say a lot more about what happened here... It is certainly leaning more in the direction that this was a specific act of terror."
New York Governor Andrew Cuomo told CNN: "I would not be surprised if we did have a foreign connection to the act."
According to CNN, surveillance videos from the Chelsea area in Manhattan show the same man near the sites of both the detonated and undetonated bombs.
He was seen dragging a duffel bag with wheels near West 23rd Street, about 40 minutes before the incident.
About 10 minutes later, he was picked up again by another surveillance camera with the same bag on West 27th Street, where he left the bag.
Soon after, two men were seen in the video removing a white garbage bag from the duffel bag and leaving it on the sidewalk.
The white garbage bag appears to contain the unexploded pressure cooker, which was examined at the FBI laboratory in Virginia.
On Sunday, Mr de Blasio urged New Yorkers to be patient while the police carry out their investigations, to remain vigilant, and to assist the police with any information they may have.
New York City Police Department Commissioner James O'Neill said the police were still gathering evidence at the site of the explosion, and had gathered some evidence "indicative of an IED (improvised explosive device)".