The US President hit out on Twitter following the confirmed terrorist attack near the new One World Trade Center in Lower Manhattan.
He wrote: “In NYC, looks like another attack by a very sick and deranged person. Law enforcement is following this closely. NOT IN THE U.S.A.!”
The First Lady Melania Trump said: “My heart breaks for #NYC today. Thoughts & prayers as we monitor the situation.”
At least eight people have died after a truck ploughed into a crowd near the site of the September 11 terror attacks.
The truck, which appears to be a Home Depot rental van, drove onto a pedestrian and cycle path alongside the West Side Highway at full speed, hitting several people.
The truck then hit another vehicle, reported to be a school bus.
4 News reported the driver then allegedly screamed ‘Allahu Akbar’ and got out of the vehicle.
He was armed with two weapons and began running before being shot by police. The weapons later turned out to be imitation firearms.
New York police have confirmed they are treating the incident as an act of terrorism.
New York Mayor Bill de Blasio said it was a tragedy of “the greatest magnitude”.
He told reporters: “The is a very painful day in our city.
“This was an act of terror, a particularly cowardly act of terror aimed at innocent civilians.”
He called on the public to be vigilant as he revealed more officers would be on New York streets in the coming days.
The mayor added: “I want to ask all New Yorkers and all Americans to keep the families of all those lost in your prayers.”
The counter-terror unit is urging people to avoid the West Side Highway area while they deal with the incident.