France fell silent today for the victims of the Nice truck attack, but the mourning was overshadowed by politicians tearing into each other over the massacre.

A sea of people thronged the Nice promenade for the emotional minute's silence just days after a Tunisian attacker drove a truck into a crowd at the same place on Bastille Day, killing 84 people and injuring around 300.

Similar gatherings were held across the country, with the minute's silence accompanied by the ringing of church bells.

Prime Minister Manual Valls was booed and faced shouts of "resign" as he arrived and left the seaside promenade in Nice, in a sign of the anger and bitterness gripping France after its third major terror attack in 18 months.

French investigators have yet to find links between attacker Mohamed Lahouaiej-Bouhlel, a 31-year-old Tunisian, and the Islamic State group which claimed responsibility for Thursday's carnage, Interior Minister Bernard Cazeneuve told France's RTL radio.

He defended government efforts to halt terror attacks, calling for "dignity and truth" from fiercely critical opposition politicians as the national mood soured further nine months ahead of a presidential election.