INVESTIGATORS ARE PROBING three attacks carried out on US soil in one day — a Manhattan bombing, a Minnesota mass stabbing and a New Jersey pipe bomb blast — for possible terror links.

Authorities say there is no evidence that the attacks were coordinated but their timing in less than 24 hours raises fears about security — already a major issue in the country’s deeply divisive presidential election battle between Hillary Clinton and Donald Trump.

Twenty-nine people were injured when a bomb exploded in New York’s upmarket Chelsea neighbourhood on Saturday night, damaging buildings, shattering glass and sending shrapnel flying across the street.

A second bomb was uncovered by police four blocks away and defused safely, before being sent to the FBI in Virginia for forensic examination.

Both bombs were filled with shrapnel and made with pressure cookers, flip phones, Christmas lights and explosive compound, The New York Times reported late last night, citing law enforcement officials.

The paper also said, citing unnamed law enforcement sources, that federal authorities detained and were questioning five people with possible links to the New York bombing.

The FBI’s New York branch tweeted that officers “did a traffic stop of a vehicle of interest” but “no one has been charged with any crime”.

The New York Daily News reported that weapons were found in the car and that one person of interest had been identified via surveillance footage, but it was not clear if he was one of the five taken into custody.

New York Mayor Bill de Blasio, left, speaks next to Police Commissioner James O'Neill, second from left, during a news conference at police headquarters yesterday. Mike Balsamo Mike Balsamo

In New Jersey on Saturday, a pipe bomb exploded in a rubbish bin on the route of a Marine Corps run before the start of the race, causing no injuries but forcing its cancellation.

On Sunday, rail service in that state was suspended between Newark airport and the city of Elizabeth, amid reports that a suspicious package had been found there. FBI officials were investigating.

In the Midwest, an assailant reported to be Somali-American went on a stabbing spree in a shopping mall in St Cloud, Minnesota, injuring nine people before being shot dead by an off-duty police officer.

US authorities said the motive of all three attacks was unclear, but elected officials quickly identified them as terror-related.

“If you look at a number of these incidents, you can call them whatever you want: they are terrorism though,” New Jersey’s Republican Governor Chris Christie, a member of the Trump campaign, told CNN.

Obama arrives in New York

“A bomb exploding in New York is obviously an act of terrorism, but it’s not linked to international terrorism,” Democratic New York Governor Andrew Cuomo said on Sunday after touring the scene of the explosion in Chelsea.

“In other words, we find no ISIS connection, et cetera,” said Cuomo in reference to the so-called Islamic State group. But he also stressed the lack of an international terror link was preliminary.

New York went on full alert, deploying nearly 1,000 extra state police and National Guardsmen to airports, bus terminals and subway stations as President Barack Obama arrived in the city ahead of tomorrow’s opening of the UN General Assembly.

There was no claim for the bombings in Manhattan or New Jersey, but a jihadist-linked news agency, Amaq, claimed that an IS “soldier” carried out the Minnesota stabbings.

IS has repeatedly called for attacks on countries in the US-led coalition bombing the extremist group in Syria and Iraq.

“This should steel our resolve to protect our country and defeat ISIS and other terrorist groups,” said Clinton, using another acronym for IS.

The Democratic nominee, whose lead in the polls has taken a dip, condemned what she called “apparent terrorist attacks.”

Trump meanwhile tweeted his “best wishes and condolences to all of the families and victims of the horrible bombing.”

‘References to Allah’

Fifteen years after the 11 September, 2001 attacks, officials stress that the United States is safer from terror plots that originate from overseas but more at risk from the lone-wolf attack perpetrated by individuals who may be inspired by IS or Al-Qaeda propaganda.

In Minnesota, FBI agent Rick Thornton confirmed that federal agents were investigating the stabbing as “a potential act of terrorism,” as local media identified the suspect as a 22-year-old Somali-American.

Police confirmed that the assailant asked some victims whether they were Muslim before attacking them and made “references to Allah.”

“In many of these cases we don’t know until two, three or four days later whether or not there is a terrorist link,” warned New York Congressman Peter King in a CBS television interview.

© – AFP 2016

Read: IS claims responsibility after man stabs 8 people in shopping mall before being shot dead >

Read: US-led coalition expresses regret after it may have killed dozens of Syrian soldiers in airstrikes >