The French government denied there was a hostage-taking incident after a truck ploughed into a crowd watching a fireworks display in Nice killing at least 70 people on Thursday.

"There is no hostage-taking," interior ministry spokesman Pierre-Henry Brandet told AFP, denying dozens of rumours following the incident.

"An individual drove a truck into the crowd. He was killed by police," he said.

"Investigations are currently under way to establish if the individual acted alone or if he had accomplices who might have fled," Brandet said.

Anti-terrorism investigators have taken over the probe, prosecutors said.