Trump vows to toughen vetting of immigrants after New York attack

President has consistently invoked terrorism to justify tighter immigration rules

US President Donald Trump has renewed his call for tougher immigration rules after a terrorist attack in New York (Alex Wong/Getty Images)

Donald Trump has responded to a terrorist attack in New York by vowing to toughen restrictions on immigration.

“I have just ordered Homeland Security to step up our already Extreme Vetting Program. Being politically correct is fine, but not for this!” the President wrote on Twitter.

Throughout his rise to the presidency, Mr Trump has invoked the threat of terrorist attacks as a rationale for tightening immigration policies, including halting refugee admissions and banning immigrants from certain Muslim-majority countries.

Mr Trump's tweets suggest that the President will double down on that push in response to Tuesday's attacks. Earlier in the day, he wrote that “We must not allow Isis to return, or enter, our country after defeating them in the Middle East and elsewhere”.

As a coalition of Iraqi troops, Kurdish forces and others have pushed Isis fighters from vast swathes of territory they seized across the Middle East, terrorism experts have cautioned that loyalists will turn to inflicting violence on Western cities.

Officials deemed the assault in New York, which left eight dead, an act of terrorism.

Multiple news outlets have reported that authorities found a note pledging fealty to Isis in or near the truck assailant Sayfullo Saipov used to mow down bystanders. New York Police Commissioner James O’Neil told reporters witnesses heard the man shout “Allahu Akbar”.

Reports said Saipov, a native of Uzbekistan, had come to America in 2010.

Courts have repeatedly blocked or diminished the President's attempted travel bans. Critics argue that those policies are inhumane or discriminatory, pointing out that the refugee admissions process already involved thorough vetting.