Expressing grief Gandhi said: "This deadly attack reflects deep resentment to peace and democratic values."
She also expressed deepest condolences to the families of those killed and called for a "strict action and harsh punishment against those who are behind the attack".
"The Congress party stands firmly with the people of France in these difficult times," Gandhi said.
At least 80 people were killed on Thursday night when a large truck mowed through a crowd celebrating Bastille Day in Nice.
French President Francois Hollande said the truck attack was of a "terrorist character".
Over 150 people were also injured in the mayhem. This was the second major terrorist attack in France after the November 13 attacks last year that left at least 130 people dead and over 250 others injured.