With Genoa just 200km away from his city, Nice mayor Christian Estrosi offered equipment to help with rescue efforts after news of the disaster broke.
The city council was in contact with the Italian consulate to find out what was needed and Nice's hospitals were ready to take people injured in the bridge collapse, he said in a statement.
Nice mayor Estrosi promises help to Genoa
Émotion à la vue des premières images du drame qui frappe nos amis italiens à #Gênes. La @VilledeNice est solidaire. J’ai demandé aux services de la Ville et au @CHUdeNice de regarder comment nous pourrions aider nos voisins. pic.twitter.com/buhl7neV9FChristian Estrosi (@cestrosi) 14 août 2018
The council in nearby Cannes also offered help, flying flags, including the Italian tricolore, at half-mast at city hall and the historic Château de la Castre.
Further along the Mediterranean coast, Marseille, which is twinned with Genoa, was "filled with sorrow" by the news, according to its mayor, Jean-Claude Gaudin.
"In the name of all Marseillaises and Marseillais, I offer my sincere condolences to the bereaved families and wish the injured a prompt recovery."
In a tweet in French and Italian, President Emmanuel Macron also offered his condolences and offered "all necessary support".
As rescuers searched for survivors and bodies on Wednesday morning, the recorded death toll rose to 38, with reports of about 16 people injured, 12 of them seriously.
Italian Transport Minister Danilo Toninelli called on the bosses of Autostrade per l'Italia, the company responsible for the bridge and much of the country's motorway network, to resign.
I nostri pensieri vanno alle vittime, ai loro familiari e a tutto il popolo italiano. La Francia è vicina all’Italia in questa tragedia e rimane pronta ad apportare tutto il sostegno necessario. #Genova #Gêneshttps://t.co/A7YAfnK3AYEmmanuel Macron (@EmmanuelMacron) 14 août 2018
In a Facebook post he announced that the government has initiated proceedings to scrap contracts with the firm, which was privatised in 1999 and is part of the Benetton group, and called for a 150 million-euro fine to be imposed on it.