France’s famous Eiffel Tower, one of the world’s most visited attractions, was closed after a man carrying a rucksack was seen scaling the tower.
The alarm was raised early on Sunday and the area was evacuated while anti-terror police carried out a search.
Police said they were unable to find the man. The landmark reopened in the afternoon, after officials carried out a search but found nothing.
France is on high alert following a series of terror attacks this year.
The Eiffel Tower, which receives as many as 30,000 daily visitors, has been the target of plots by Islamist extremists in the past.
But police said there may be another explanation for Sunday’s security breach – the man may have been a parachutist hoping to perform a jump.