The French prime minister was jeered by a large crowd as he attended a minute's silence to remember victims of the attack in Nice. Boos rang out as Manuel Valls joined thousands on the city's seafront, which had been the scene of carnage on Thursday (14 July) when an attacker ploughed a 19-tonne lorry into people celebrating Bastille Day.
Eighty-four people were killed and 85 remain in hospital, 18 of them in critical condition. The attacker, 31-year-old Tunisian delivery driver Mohamed Lahouaiej-Bouhlel, was shot dead by police in the immediate aftermath.
As crowds placed flowers alongside photographs of victims in Nice on Monday (18 July), Valls was twice booed with some hecklers chanting "resign" and "murderer".
The French government has been criticised by political opponents for what they said had been an ineffective counter-terrorism policy, while President Francois Hollande's popularity ratings remain at the lowest ever for a modern leader in France.
The Nice attack was France's third major Islamist attack in 18 months, and came eight months after the November Paris attacks that left 130 dead.
Former French President Nicolas Sarkozy, leader of the Republicans, said France's government was at war with violent jihadists and accused ministers of confronting them with "trembling hands". He called for extra security measures, including deporting all foreign nationals with links to radical Islam.
Interior Minister Bernard Cazeneuve said no links had yet been discovered between Lahouaiej-Bouhlel and terrorist networks, despite the Islamic State (IS) claiming responsibility. The authorities said the attacker may not have been placed on a terrorist watch list because he had only recently been radicalised.
Neighbours described Lahouaiej-Bouhlel as a violent loner who smoked, drank alcohol and seldom visited mosques. Questions have also arisen over his mental health.
"We cannot exclude that an unbalanced and very violent individual, and it seems that his psychology demonstrates these traits, was at one time, in a rapid radicalisation, committed to this absolutely appalling crime," Cazeneuve said on Monday (18 July).
He went on to dismiss criticism of his response to the heightened terror level, saying that France was facing "a new kind of threat" that highlighted "the extreme difficulty of the anti-terrorism fight".
So far, French police have arrested six people in connection with the attack. The latest, an unnamed Albanian couple suspected of providing the firearm used by Lahouaiej-Bouhlel during the attack, were detained on Sunday (17 July) morning. The attacker's estranged wife, detained on Friday (15 July), has since been released.
France has called up 12,000 police reservists to relieve the pressure on the country's overextended security agencies, with Cazeneuve urging "French patriots" to join the force as volunteers.
EU foreign ministers, joined by US Secretary of State John Kerry, have meanwhile gathered at a summit in Brussels to discuss the fight against terrorism in Europe.