French army Eiffel tower
The French army guard the Eiffel Tower in the wake of the Charlie Hebdo attacksGetty Images

France's iconic tourist attraction, the Eiffel Tower was shut to tourists and visitors after a suspicious male carrying a large rucksack was seen going up the building. Anti-terrorist police and a helicopter were at the scene after an alarm was raised at 9am on Sunday, (20 September).

"There's been a report of a man with a rucksack," said a police source assisting with the evacuation of the tower. The man was spotted at the French landmark more than an hour before it opened, said a police source. But a search for the unidentified male failed to apprehend him and in the early afternoon, his whereabouts were still unknown.

A police cordon was place around the tower and people were moved to the banks of the nearby River Seine. Crowds of hundreds of people were attempting to go up, but were told to leave the area, with ticket booths closed to the public.

The Eiffel Tower has often been threatened by terrorist groups, including Isis and al-Qaeda, with security stepped up since attacks by three radical Islamist gunmen in the city in January. France is currently on the highest state vigilance alert.

France stopped an attempted Islamist terrorist plot to target the Eiffel Tower in 2014. French police came across plans after decrypting coded messages between a 29-year-old Algerian butcher living in the Vaucluse, southern France, known as Ali M, and one of the highest-ranking members in al-Qaeda. According to Le Parisien newspaper, Ali M suggested targeting nuclear power plants, "planes at the moment of take-off", and a string of French landmarks, including the Eiffel Tower.

Police believe that an alternative explanation is that he might be an extreme parachutist hoping to jump off the building. "It's happened in the past," said the same police source. "The parachutist hides his kit the night before, and then gets into the tower and jumps off, while videoing." In 2005, a Norwegian parachutist died while attempting to jump off the tower.