The Eiffel Tower has been evacuated after a person was spotted climbing up the Paris landmark, the company that operates the structure said.
A person could be seen dangling just below the third and highest level of the structure. A rescuer dressed in red was just above him.
"A climber has been spotted. It's the standard procedure: We have to stop the person, and in that case we evacuate the tower," an SETE official said.
"We kindly advise our visitors to postpone their visit," the SETE added on Twitter.
Police said the climber was a male.
It wasn't immediately clear how the trespasser managed to get past the stringent security system.
A Paris police spokeswoman said a team of firefighters including a climbing specialist was on the scene and in touch with the intruder, whose motivations remain unclear.
The esplanade underneath the monument was also evacuated.
Police have made contact with the climber but do not yet know why he began his ascent via the iron beams, a police source told AFP.
In October 2017 the tower was also evacuated after a young man ventured out on one of the beams and threatened to commit suicide, before police were able to convince him to come back.
Nearly seven million people a year visit the 324-metre-high structure, which last week celebrated its 130th anniversary.
The first two floors can be reached by either elevator or stairs, but only elevators whisk people to the top observation deck.
It's not the first time a daredevil has attempted the feat. In 2015, British "freerunner" James Kingston climbed the edifice without safety ropes and without permission, dodging security cameras as he went.