Francois Fillon, former French Prime Minister, member of the Republicans political party and 2017 French presidential election candidate of the French centre-right, attends a political campaign rally in Lille, France, April 18, 2017. REUTERS/Pascal Rossignol

PARIS (Reuters) - French conservative presidential candidate Francois Fillon on Thursday evening said he was cancelling a planned election campaign outing on Friday after a shooting in Paris which killed a policeman.

The circumstances of the shooting, in which an assailant was also killed, were not immediately clear.

Voters are set to head to the polls on Sunday in the first round of a two part election, and campaigning by the 11 candidates in the running was due to be wrapped up on Friday.

Fillon had been scheduled to go to the French Alps for a campaign event but told France 2 television he would not go.