Security sources in Paris reported that at least five drones were spotted in the skies above Paris in the early hours of Tuesday morning.

Although nothing sinister happened the mysterious flights will no doubt trouble security chiefs who are in charge of protecting a French capital that is on edge after January’s terror attacks.

The locations, including the Eiffel Tower, the Montparnasse tower and the US embassy, appear to have been chosen specifically to cause maximum alarm among already twitchy security chiefs.

“It could be coordinated action, but we don’t know,” a source close to the investigation told AFP, adding “We did everything to try and catch the operators, but they were not found.”

French aviation and air safety expert Christophe Naudin told The Local he believes whoever is behind the drone flights in Paris were also behind the 20 or so flights over France’s nuclear power stations last year.

“My hypothesis would be that it is some kind of ‘eco-terrorist’ group, who want to demonstrate how the state is incapable of reacting against this new kind of threat,” he said.

“It appears to have been a very well organised operation, involving several drones, that may have been operated manually or on pre-programmed flights,” he said.

“It was done to ridicule the state and the forces of law and order and to show they are not capable of protecting the population.”

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Naudin points out the type of drones used were not ones flown by amateurs to take films, "they are used by real pros.”

“They did the same last year with the drones over nuclear power stations, but it didn’t really work because there’s no real threat of a radiation leak if they crashed into the facility,” he said.

“But now they have decided to do the same over densely populated cities, where the public will be more fearful that the drones could be carrying a product that can be dispersed,” Naudin added.

After the flights over the nuclear plants, the finger of blame was immediately pointed at environmental group Greenpeace, who have carried out regular protests to highlight a weakness in security at the country’s power stations.

Naudin believes a more extremist group, with possible links to Greenpeace, is more likely to be behind the drone stunts.

With the fresh sightings coming just weeks after the terrorist shootings rocked the city, police will be taking any kind of security threat seriously.

The expert believes for the moment the drones are harmless enough, but that won’t be the case in the future and it should be a wake-up call for authorities.

“We have a real problem because we are not ready to tackle this form of threat. Today drones are not a problem but in three or four years they will be, because their capacity to transport things, like explosives, will be much higher," Naudin said.

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"One day they will be used for something dangerous," he said. "Currently drones are not developed enough to be able to carry something like a grenade or a bomb but in the years to come they will be. At the moment terrorists don't have the training to be able to use them, but that won't always be the case.

"Drones will be available to buy on the international black market and anyone will be able to learn to fly them."

Even though police spotted one of the drones above the US embassy they lost sight of it as they tried to follow it towards the Invalides military museum.

“It’s almost impossible to keep track of a drone in a city,” said Naudin. “If you were in the countryside it would be easier but not in Paris. You can’t follow it from one building to another, even in a very cast car.”

While those behind Tuesday's drone flights got away, we can expect them to reappear at some point in the future, especially given the frequency the flights were carried out over nuclear stations last year.

Meanwhile France does appear to be concerned about a future threat from drones and recently launched a €1 million ($1.1-million) programme aimed at developing ways of detecting and intercepting them.