A prestigious Argentine school was in shock today after five of its alumni were among those killed in the truck attack in Lower Manhattan.

Students at the Politecnico de Rosario secondary school - in the city of Rosario, some 350 kilometers northwest of Buenos Aires - began the day with a minute of silence honouring the victims, who died in yesterday's attack that killed a total of eight people.

The school board decreed five days of mourning with the flag at half-mast to honor slain alumni Alejandro Pagnucco, Ariel Erlij, Hernan Ferruchi, Hernan Mendoza and Diego Angelini.

The killings "affect everyone" because of the strong camaraderie in the school community, said Politecnico graduate Laura Racca, class of 1987.

Gone is "that sensation that nothing will ever happen to you coming from Argentina, and being far away from wars and terrorism," Racca said.

The victims, all successful businessmen and architects, were visiting New York for a 30-year graduation reunion along with five other alumni.

One of the survivors, Martin Ludovico Marro, was hurt in the attack and being treated at the Presbyterian Hospital in Manhattan with non-life-threatening injuries.

Silvia Goldberg, the mother of a teenage Politecnico student, said she was speechless when she saw the news on television.

"I couldn't believe it," she said. "I'm most saddened because they went there to celebrate their friendship."

President Mauricio Macri, who had earlier expressed his condolences to the families of the victims, on Wednesday described the victims as "five young entrepreneurs, members of Rosario society."

The attack "is something that has hit all of us Argentines hard and especially me," Macri said as he opened a financial forum in Buenos Aires.