Authorities in Nice have refused a request from French anti-terror police to delete surveillance camera images of last week’s deadly truck attack, amid growing questions over the scale of the police presence at the time.

The city received a letter this week from the SDAT anti-terrorism agency asking for images of the 14 July attack to be destroyed, an official at Nice city hall said on Friday.

The city is filing a legal complaint instead, arguing that the images could constitute evidence in the case, said the official, who is not authorised to be publicly named.

The letter did not provide a reason for the request, the city official said, but Le Figaro newspaper said national police were concerned the images would leak out and be used for jihadi propaganda.

The request came as the government faces growing criticism over security measures on the night of the attack, and the cameras could show where and how police were deployed.

Regional official Christian Estrosi, of the conservative opposition Republicans party, had argued for tougher security for Nice’s Bastille Day fireworks celebrations.

The interior minister, Bernard Cazeneuve, acknowledged on Thursday that only lightly armed local police were guarding the entrance to a pedestrian zone on the Nice beachfront when driver Mohamed Lahouaiej Bouhlel sped past a barricade and ran over 84 people. Cazeneuve had previously said national police were guarding the closed-off boulevard.

An internal police investigation into the security measures has been launched and President François Hollande is holding a special security meeting on Friday.

Five people were handed preliminary terrorism charges late on Thursday night. The Paris prosecutor says Bouhlel had accomplices and appears to have been plotting his attack for months, citing text messages, more than 1,000 phone calls and video of the attack scene on the phone of one of the suspects.

Nice city hall has put up the names of all 84 people killed in the attack on two black banners. The victims were of several nationalities, as were the more than 300 people wounded in the attack.