PARIS (Reuters) - Police evacuated Paris' Notre Dame cathedral on Tuesday after a well-known far-right former activist committed suicide by shooting himself in the mouth in front of its main altar, a police source said.

The man, 78-year-old Dominique Venner, is a historian known in France for his far-right political essays. He carried a letter on his person but made no declaration before shooting himself dead in the mid-afternoon, the source said.

A note posted on his blog dated May 21 slammed a law passed by the Socialist government last week allowing same-sex marriage.

Notre Dame is one of Paris' most visited tourist attractions.

(Reporting by Nicolas Bertin; Writing by Nick Vinocur; editing by Mike Collett-White)