The unnamed climber, who used no harnesses or other aids, was detained after he got to the top of the 210-metre (690 feet) office block, the source said.
He began the ascent in the early evening and was arrested at 8:00 pm (1800 GMT) after a rescue worker descended on a rope and accompanied him to the roof of the tower.
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It wasn't the first time a climber had taken on the Tour Montparnasse. In 2015 the French “Spiderman” Alain Robert completed the daring feat with a Nepalese flag in hand, in tribute to the victims of a devastating earthquake in the country.
The Tour Montparnasse is not as high as the famous Eiffel Tower but remains the only skyscraper in the Paris city centre.
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The security services' DOPC intervention and protection group (Gip) abseiled down to reach the man.
Francois MALIGORNE / AFP