A far-right French historian shot himself in the head beside the altar of Notre Dame cathedral in Paris today apparently in protest against the legalisation of gay marriage in France.

Dominique Venner, 78, a former member of the nationalist terrorist movement, OAS, placed a pistol in his mouth and shot himself dead in front of scores of tourists inside the most visited building in France.

Mr Venner, a presenter on a Catholic-traditionalust radio station and controversial historian and essayist, posted an essay on his website earlier in the day calling for "new, spectacular and symbolic actions to shake us out of our sleep, to jolt anaesthetised minds and to reawaken memory of our origins".

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His long essay was a tirade against gay marriage but also a warning that the "population of France and Europe" was going to be "replaced" and brought under "Islamist control" and "sharia law".

Mr Venner placed a sealed letter on the altar of the cathedral before shooting himself. His choice of the altar - associated with religious marriage ceremonies -appeared to be a symbolic gesture of protest against the law permitting civil gay marriages in France which took effect last weekend.

The cathedral, which is celebrating its 850th anniversary this year, was immediately evacuated and closed to the public for four hours. Efforts were made by a cathedral security guard to revive Mr Venner as he lay beside the altar for almost 20 minutes.

The rector of Notre Dame, Monsigneur Patrick Jacquin, said that, as far as he was aware, this was the first suicide within the cathedral since it was founded in the 12th century. "We will pray for this man as we pray for so many others who are at their wits' end," he said.

Notre Dame is the most visited monument in France with over 13,000,000 visiors a year. The building was, as usual, packed with tourists at the time of Mr Venner's suicide.

Legislation permitting same-sex couples to marry in French town halls was approved by the parliament last month and signed into law by President François Hollande last weekend after approval by France's constitutional watchdog.

The "marriage for all" law has provoked a powerful movement of middle class, conservative, religious and right-wing protest in the last four months. Another large demonstration is planned in Paris on Sunday.

The leaders of the protest movement, including most but not all leading centre-right politicians, have pilloried the law as politically-motivated attack on family and religious values and the imposition of a "new civilisation".

Mr Venner, a prolific author of books and tracts on extreme nationalist themes, has been one of many vociferous critics of the law. Some of his work as a historian has been well-received, incuding a 1981 book on the Red Army which won a prize from the Académie Française. Much of his work has been steeped in the racist ideology of the far-right, apologising for the pro-Hitler regime in Vichy in the Second World war and warning of conspiracies to destroy European civilisation and to swamp the white race.

Mr Venner was also an expert, and the author of several books, on hunting and fire-arms. In the 1960s, he was a member of the Organisation de l'Armée Secrète - the extreme nationalist terrorist movement which opposed the French withdrawal from Algeria and attempted several times to assassinate President Charles de Gaulle.