The move was largely expected given what they had said in advance of the strike.
Unions voted on Thursday to prolong the strike action meaning transport in the French capital will be severely disrupted until Monday at least.
Nearly all the striking workers voted to remain off the job until Monday, Thierry Babec of UNSA union said, adding that the network would remain “at a virtual standstill” if the government did not abandon the reforms.
Laurent Djebali had warned in Le Parisien newspaper earlier this week that the most important day for them was not Thursday or Friday or even the weekend.
“The crucial day is Monday,” he said. “We are ready to carry on until Christmas.”
The tweet below shows which lines will be most disrupted on Friday.
— The Local France (@TheLocalFrance) December 5, 2019
Unions and the government will be watching closely how well supported the strikes are on Monday compared to Thursday as this will give a sign as to how long they might go on for.
On Thursday some 11 Metro lines were completely closed while others only operated during rush hour.
Only lines 1 and 14 were fully operational because driverless trains operate on that line.
Only one in three busses were running in Paris on Thursday.
Service on the heavily used suburban rail lines crossing the city and on buses and trams were also heavily disrupted.
Anticipating the worst travel chaos in years, many employees were working from home on Thursday. Those who did venture out travelled mainly by car, bicycle, electric scooter or on foot.
People in Paris can expect a similar situation on Friday and over the weekend until Monday.