Venner, 78, walked into the Paris cathedral Tuesday, placed a letter addressed to investigators on the altar and shot himself through the mouth as an estimated 1,500 people toured the building, the British newspaper The Guardian reported.
Police Wednesday arrested a member of Femen, a feminist organization based in Kiev, Ukraine, after she staged a mock-suicide, while topless, at the cathedral.
The woman -- identified only as Marguerite -- held a pistol in her mouth and displayed the words "May fascism rest in hell" on her torso, The Guardian said.
"Femen appealed for the death of fascism at the exact same place extreme-right activist Dominique Venner committed suicide yesterday afternoon," the feminist organization said in an online post.
"It is a message addressed to all those who support fascism and those who have expressed sympathy for the extreme-right militant who killed himself in Notre Dame -- namely Marine Le Pen," Femen leader Inna Shevchenko said.
Venner had written a letter to friends, saying his physical and mental health were sound, the newspaper reported.
"I expect nothing more from life except the continuation of my race and my spirit," he wrote. "However, at this, in the evening of that life and in the face of immense dangers for my French and European heritage, I feel the need to act, while I still have the force. I believe it is necessary to sacrifice myself to break the lethargy that oppresses us. I offer what remains of my life in an act of protest."
Le Pen, head of the far-right Front National party, said on Twitter Venner's death was an "eminently political" gesture.
Venner, a noted far-right essayist, had written a blog post Tuesday condemning the Saturday passage of same-sex marriage legislation in France, The New York Times reported.
He called the new law "vile," and railed against what he called an imminent takeover of France by Muslims.
"New, spectacular and symbolic gestures will surely be needed to rattle the somnolent, shake anesthetized consciences and reawaken the memory of our origins," he wrote. "It is in deciding by oneself, in truly desiring one's fate that one is triumphant over the void."