Censor.NET reports citing BBC.
A single gunman armed with an automatic weapon opened fire on a foot patrol before being killed in turn, according to Le Parisien newspaper citing its own sources.
The whole of the Champs Elysees has been evacuated and police vehicles are lined up near a point half way up the avenue around the George V metro station, a BBC correspondent says.
An anti-terrorist investigation has been launched.
It happened as candidates made their last pitches in a TV appearance before Sunday's presidential election.