Eight people were killed and 11 injured when the driver of the truck hit people on a cycle path in Lower Manhattan.
A 29-year-old man, reported to be an Uzbek immigrant, was shot and injured by police as he left the vehicle.
US President Donald Trump has ordered the Department of Homeland Security to "step up" vetting measures in the wake of the attack.
The suspect reportedly shouted "Allahu Akbar" ("God is greatest") as he left the truck. Officials said it was a terror attack.
A note was found in the truck that referred to so-called Islamic State, law enforcement sources were quoted as saying by US media.
Who were the victims?
The deaths of the five Argentines were confirmed by the country's foreign ministry. They were part of a group of 10 friends in New York to celebrate the 30th anniversary of their graduation from a polytechnic college in the central city of Rosário, Argentine media said.
Argentina's foreign ministry named the men - all reportedly aged 48 or 49 - as Diego Enrique Angelini, Alejandro Damian Pagnucco, Ariel Erlij and Hernan Ferruch. Another of the friends, Martin Ludovico Marro, is being treated in hospital.
Three days of mourning have been called in Rosário, Clarín newspaper reported. President Mauricio Macri expressed his "deep condolences" for the victims' families on Twitter.
A Belgian national was also killed, Belgium's foreign minister said. Two other victims have not yet been identified.
How did the attack unfold?
At a news briefing, New York Police Department (NYPD) Commissioner James O'Neill said:
 Shortly after 15:00 local time (19:00 GMT), a white pick-up truck rented from retailer Home Depot struck cyclists and pedestrians while being driven along the West St-Houston St path for many blocks
 The vehicle then hit a school bus, injuring two adults and two children on board, and came to a halt
 The driver emerged holding what appeared to be two handguns and made a statement "consistent with a terror attack"
 He was shot in the abdomen by a police officer stationed near the scene
 A paintball gun and a pellet gun were recovered from the scene
Mangled bicycles littered the scene of the attack, which occurred as much of the city was celebrating Halloween.
One witness, identified as Eugene, told ABC Channel 7 that he saw the white pick-up truck driving fast down the cycle path alongside the West Side Highway, near Stuyvesant High School, at full speed and hitting a number of people.
He also reported hearing about nine or 10 shots.
Another witness, who gave his name as Frank, told local TV network NY1 that he had seen a man running around an intersection and heard five to six gunshots.
"I saw he had something in his hand, but I couldn't tell what it was. But they said that it was a gun...
"When the cops shot him, everybody started running away and it got a little bit crazy right there. So when I tried to look again, the guy was already down."
What has been the reaction?
President Trump had been briefed about what happened in New York on Tuesday afternoon, the White House said.
He also announced that he had ordered the Extreme Vetting Program to be stepped up. He did not elaborate further.
Meanwhile, New York City Mayor Bill de Blasio said the incident in Manhattan was a "cowardly act of terror aimed at innocent civilians".
"We know that this action was intended to break our spirit. But we also know that New Yorkers are strong, New Yorkers are resilient and our spirit will never be moved by an act of violence and an act meant to intimidate us," he said.
What is known about the suspect?
The NYPD said only that the attacker was a 29-year-old man.
However, US media named him as Sayfullo Saipov, who had reportedly lived in Tampa, Florida, and Paterson, New Jersey.
He arrived to America from Uzbekistan in 2010 and is believed to be a legal resident in the country. Car-share service Uber confirmed he had been working for them.
Three officials said Mr Saipov had previously come to the federal authorities' attention as a result of an unrelated investigation, the New York Times reported.
Police records show he was arrested in Missouri last year over a traffic fine.

Source: BBC