Estonia's foreign ministry on Tuesday morning said it had received confirmation from French authorities that two Estonians were among the dead.
It was previously reported that four Estonians were among the injured.
"I express my heartfelt condolences to the families of the Estonian citizens who have lost loved ones in the terrorist attack... This is the first time that terrorism has affected us all so painfully and directly. I have no words to describe the sadness and pain this brutal tragedy has caused to so many," said Estonian foreign minister Marina Kaljurand.
Latvian Prime Minister Maris Kucinskis on Tuesday tweeted his condolences and said Latvia stood together with Estonia.
My deepest condolences to the families of Nice terror act victims. We are together with Estonia in this tragedy.— Maris Kucinskis (@MarisKucinskis) July 19, 2016
Latvia's embassy in Tallinn added its voice, too, writing "We are with you!" in Estonian:
Our deepest condolences to the Estonian victims of the terror attack in Nice, their families and friends. Oleme teiega koos!— Latvia in Estonia (@LV_Estonia) July 19, 2016
Foreign minister Edgars Rinkevics said "your pain is our pain"
We are grieving together with our Estonian friends and neighbours over the loss of lives in #NiceAttack, your pain is our pain— Edgars Rinkēvičs (@edgarsrinkevics) July 19, 2016
Four Estonians were among the scores of people killed and injured when a deranged individual drove a truck into crowds celebrating Bastille Day.
We at LSM would also like to offer our condolences to our friends in Estonia.