Witnesses said that the man had placed a letter on the altar of the church before shooting himself in the head just after 3 p.m. on Tuesday.

The suicide was hailed as a political gesture by Marine Le Pen, leader of France's far-right National Front. "All respect to Dominique Venner whose final, eminently political act was to try to wake up the people of France," Le Pen said on Twitter, signing her initials to indicate that she had written the entry personally.

Le Pen's far-right party, running primarily on an anti-immigration platform but which also opposes French government efforts to legalize gay marriage, is the third-most popular in the country.

The man was identified by police as 78-year-old Dominique Venner, a historian known for his far-right publications. A note on Venner's blog, dated May 21st, had strongly criticized a law to allow same-sex marriage that was passed by the Socialist government last week.

Venner - a paratrooper during France's war in Algeria - had written essays, military histories and books about weaponry and hunting.

'Need for gestures'

In the blog piece that saw him rail against the adoption of the gay marriage law, Venner called for words to be followed with deeds. "There will certainly need to be new, spectacular, symbolic gestures to shake off the sleepiness... and re-awaken the memories of our origins," Venner had written.

Police told the agency that the contents of the letter echoed comments posted on Venner's website.

Visitors to the cathedral were cleared from the building after the incident took place. "It's unfortunate, it's dramatic, it's shocking," Monsignor Patrick Jacquin told the AP news agency. "We did not know him, he was not a regular at the cathedral."

Jacquin said that, while a number of people had taken their own lives by jumping from the cathedral's twin towers, he had no knowledge of anyone committing suicide on the altar.

The 850-year-old Gothic cathedral, which lies on an islet on the River Seine, is one of the most visited sites in Paris, attracting 13.6 million visitors in 2011.

rc/msh (AFP, AP,dpa, Reuters)