'Terror' bomber strikes New York subway, 3 hurt

Police stand in a closed-off underground walkway near the site of a pipe bomb explosion in New York City. (John Moore/Getty Images/AFP)

Akayed Ullah told police investigators he wanted to avenge US airstrikes on the Islamic State group and was also inspired by Christmas terror plots in Europe, and chose the location for his attack by the Christmas posters on the subway walls, US media reported.

His bomb failed to detonate properly, leaving him the only one seriously injured in the incident.

President Donald Trump used the attack to call for tougher US immigration rules, saying the current "lax" policy "allows far too many dangerous, inadequately vetted people to access our country."

"Today's attempted mass murder attack in New York City - the second terror attack in New York in the last two months - once again highlights the urgent need for Congress to enact legislative reforms to protect the American people," Trump said in a statement.

BOMB ONLY PARTIALLY DETONATED

The blast took place in the subway station at the Port Authority bus terminal, not far from the city's iconic Times Square, sparking commuter panic and travel disruptions.

A closed-circuit security video showed commuters scattering as the bomb exploded and one body - that of the bomber - on the ground after the smoke cleared.

Authorities attributed the minimal damage from the simple device attached to Ullah's chest to a malfunction.

The explosion left him with several burns to his torso and hands, and he was sent to a hospital in "serious" condition.

The other three injured people suffered ringing in the ears, headaches and other minor complaints, and there was no significant damage to the subway structure.

"Fortunately for us, the bomb partially detonated," New York Governor Andrew Cuomo said. "It did not fully have the effect that he was hoping for."

Cuomo said Ullah was not part of a "sophisticated network," but appeared to have been "influenced" by the Islamic State or other extremist groups.

CHRISTMAS ATTACKS THREAT

The attack came as the Christmas-New Year holiday season was moving into high gear, underscoring the possible threat that lone actors inspired by Islamic State or Al-Qaeda pose to festive crowds.

In Berlin last year, an IS-inspired Tunisian refugee drove a large truck into a crowd at a Christmas market, killing 12.

Islamic State supporters have made online threats and urged sympathisers to conduct attacks on Western targets during the holiday season.

New York was rocked on Oct 31, the Halloween holiday, when an immigrant from Uzbekistan drove a rented truck down a busy bike and pedestrian path, killing eight people and injuring 12.

In November, the US State Department issued an alert for travelers to Europe during the holiday season, reminding them of the Berlin attack as well as the assault on a New Years Eve party in an Istanbul nightclub last year that left 39 people dead.

"US citizens should exercise caution at holiday festivals and events," the State Department warned.

"Extremists continue to focus on tourist locations, transportation hubs, markets/shopping malls and local government facilities as viable targets."

Cuomo said the latest bombing underscored that New York is a perennial target, 16 years after the 9/11 attacks.

"This is New York. The reality is that we are a target by many who would like to make a statement against democracy, against freedom," he said.

A bomb in a subway station "is in many ways one of our worst nightmares," Cuomo said.

TRUMP DEMANDS TIGHTER IMMIGRATION

The White House quickly turned the attack into a justification for its crackdown on immigration, which has seen the Trump administration slash refugee arrivals, block travelers from six Muslim-majority countries, and press for tighter restrictions on all those seeking to legally move to the United States.

Sayfullo Saipov, the Halloween attacker, had entered the country in 2101 under the "Diversity Immigrant Visa" program, by which the United States has sought to widen the sources of immigrants.

Ullah arrived seven years ago as the member of a family already in the United States, under what is known as "chain immigration."

Trump has called to eliminate both programs and move to a merit-based immigration policy.