A noise that sounded like gunfire sparked panic at a French Riviera resort as people rushed to flee what they believed was a terror attack, causing a number injuries, the fire service said.

The noise was caused by firecrackers thrown from a car, local radio France Azur reported, adding that around 40 people were injured in the incident late Sunday in Juan-les-Pins.

Video footage showed tables and chairs overturned on the terraces of cafes and restaurants near the beach and people screaming in the stampede.

The incident came amid heightened tension in France after a string of attacks claimed by the Islamic State group, including the July 14 massacre in the Mediterranean city of Nice when a Tunisian ploughed a truck into crowds celebrating Bastille Day, killing 85 people.

A state of emergency was declared in France after November's IS attacks in Paris which left 130 people dead.

The fire service in Juan-les-Pins, known for its vibrant nightlife and annual jazz festival, said a number of people were lightly injured but did not say how many.

Police were examining CCTV footage to determine the exact cause of the incident.

The Nice Matin newspaper quoted witnesses as saying beachgoers rushed into the streets of the busy nightlife area on hearing what they feared was gunfire.

One witness told AFP he saw "a lot of people running" in a "stampede caused by the panic" that "left dozens of people slightly injured".

The injured were treated at the scene, some in the restaurants, and "police cordoned off the town centre," he said.

In New York on Sunday, unfounded reports of shots fired at the city's main John F. Kennedy airport triggered scenes of panic, evacuations and huge flight delays.