US officials said eight people died and eleven others were seriously injured in the first deadly attack on the city since the September 11, 2001 Al-Qaeda hijackings.
"I am deeply saddened to announce a Belgian victim in Manhattan -- I express my condolences to the family and friends," Reynders said on Twitter.
"My thoughts are with the victims of the attack in New York," he said, without giving further details about the victim.
The truck driver struck just blocks from the 9/11 Memorial, on the West Side of Lower Manhattan, and close to schools and a park at 3:05pm (1905 GMT)) as children and their parents geared up to celebrate Halloween.