A gunman who shot dead at least two people in the center of the French city of Strasbourg was known to France's internal security services as a suspected security risk, the local police prefecture said in a statement.

Some 26,000 individuals suspected of posing a security risk to France are on the Fiche S watch list, of whom about 10,000 are believed to have been radicalized, sometimes in Salafist mosques, online or abroad.