Washington, Nov 1 (IANS): US President Donald Trump has ordered extreme vetting of foreign nationals after it was revealed that the perpetrator of an attack in New York City that killed eight people was an immigrant from Uzbekistan.

"I have just ordered Homeland Security to step up our already Extreme Vetting Programme. Being politically correct is fine, but not for this!" Trump wrote on Twitter on Tuesday night.

The President did not specify which programme he was referring to in his tweet nor the measures it entailed.

The White House also did not offer any explanations regarding the announcement.

A few hours earlier, Trump had referred to the Islamic State terror group in another tweet although the organisation has not yet claimed the New York City attack.

Police found a note left by the alleged attacker vowing allegiance to the Islamic State (IS).

"We must not allow ISIS to return, or enter, our country after defeating them in the Middle East and elsewhere. Enough!" Trump wrote.

The US media identified the suspect of Tuesday's multiple hit-and-run in New York City as Sayfullo Saipov, a 29-year-old Uzbek national.

According to ABC News, Saipov entered the US seven years ago under a programme which offered a lottery for people from countries with few immigrants to America.

According to witnesses of the incident, the attacker yelled "Allahu Akbar" ("God is great") when he came out of the pickup truck he was driving after it crashed into a school bus after he had run over dozens of people.