France, Feb. 28 -- French Prime Minister Jean Castex has called on police chiefs in20 departments under heightened surveillance threatened by an explosion of coronavirus cases to crack down on citizens flouting the rules aimed at stemming the spread of the illness.

The disease, which has killed just over 86,000people in France since January 2020, shows no signs of abating despite the imposition of a nationwide curfew and a large take-up of staff using their computers at home to avoid travelling on public transport and going into the office.

The 20 zones include the Pas de Calais in the north, Paris and several of departments surrounding it as well as the Moselle in the east and the Var to the south.

Castex emerged from a meeting on Sat...