Three Al Jazeera journalists have been arrested for allegedly flying a drone aircraft over the Bois de Boulogne park in Paris.

Police said that - "for the moment" - there was no connection with other unexplained nightime sightings of drones over the city.

"The first was piloting the drone, the second was filming and the third was watching," a police source told France's AFP news agency.

The people arrested are aged 34, 52 and 68 but their names and nationalities have not been disclosed.

Al Jazeera has so far made no comment

At least five drone have been spied during the last two nights at locations including the US Embassy, the Eiffel Tower and major thoroughfares in central Paris.

The unmanned aircraft are said to have been reported by witnesses and security forces.

Paris is on high alert after the Charlie Hebdo terrorist attacks last month.

However, government spokesman Stephane Le Foll warned against scaremongering: "People should not be worried but vigilant, it's an issue which is taken very seriously."

Flying drones over the French capital requires permission from authorities but none was sought for any of the recent sightings.

The reports are the latest in a series of unexplained drone flights over the city and elsewhere across the country.

Authorities were first alerted to mystery drone flights in October, when state-run power company EDF filed a complaint with police.

The company had detected tiny unmanned planes buzzing around the skies above seven atomic plants.

The sightings continued into November, and altogether some 20 flyovers took place near nuclear plants.

In January, a pilotless aircraft also flew over the presidential palace in Paris.

Sensitive areas are protected by a no-fly zone that spans a 1.6-mile radius to a height of 1,000 metres.