Crowds have jeered France’s leaders at a tribute to victims of last week’s truck attack in Nice, as an opinion poll shows a sharp drop in confidence in the ability of President Francois Hollande’s government to combat terrorism.

Before and after a minute of silence held to pay respects to the 84 dead on Monday, many of the thousands gathered in the south-coast resort city of Nice chanted “resign, resign” at Manuel Valls, the Socialist prime minister. Others yelled “Hollande, resign”.

Watch the crowd reaction:

https://www.youtube.com/watch?v=24eYrxLHUrc

The poll published in Le Figaro newspaper showed 33 per cent of respondents were confident in the current leaders’ ability to fight terrorism, down sharply from confidence levels of at least 50 per cent in the wake of two major attacks last year.

“The government promises us things but nothing sticks,” Nice city resident Antony Fernandez told Reuters. “What have they done up to now to make us feel safe? And yet what do we expect? Every six months we’re going to mourn for more dead?”

The latest poll came at a moment when, less than a year from a presidential election, political opponents have fast abandoned the initial restraint that usually prevails on such occasions to sharply criticise Hollande and his government.

Ex-president Nicolas Sarkozy, who is competing in a November primary for the ticket to run as presidential candidate for France’s mainstream centre-right parties, said overnight that Hollande’s government had failed to do all it could.

“Everything that should have been done over the last 18 months … wasn’t done,” he told TF1 TV.

In Thursday’s attack, delivery man Mohamed Lahouaiej Bouhlel ploughed a 19-tonne truck into crowds of revellers, killing 84.

He was shot dead by police. The killings plunged France back into a state of grief, fear, and now political recrimination.

People gather at a makeshift memorial to observe a minute of silence to honour the victims of an attack in Nice. Photo: AAP

As tributes drew throngs of people back to the scene of the carnage, police investigated, with some four of the six people arrested after the attack transferred early on Monday for questioning at the headquarters of France’s counter-terrorism department in the western edge of Paris.

Paris Prosecutor Francois Molins, who is in charge of the investigation, said the attack was premeditated.

Bouhlel on June 28 had tried to get a 5000-euro ($A7,272) bank loan, which he was denied.

From July 1, he had also made internet searches for festivities in Nice and had driven the route of the attack two days before Bastille Day.

Molins said the killer had recently developed an interest in radical Islam telling people he had grown a beard for religious reasons and that he could not understand why Islamic State could not have its own territory.

Bouhlel had also carried out daily searches from the start of July of jihadist propaganda websites showing violent images.

“While there are no elements in the investigation to suggest at this stage an allegiance to Islamic State nor links with individuals from the group … he (Bouhlel) showed a certain recent interest in radical jihadist movements,” Molins said.