Workers at France's state utility EdF have cut power supplies to five nuclear power stations in protest against the partial sell-off of their firm.
The strike action looks set to continue
Workers cut output by 5,700 megawatts - said to represent 10% of capacity - and severed an export cable to Spain.
The workers fear the privatisation move could lead to job losses.
They have warned that the strike action - which has included cutting power to the home of Prime Minister Jean-Pierre Raffarin - may go on until 14 July.
Network investment required
EdF and Gaz de France employees walked out on Tuesday, as a parliamentary debate began on a bill to transform utilities into limited liability companies, a move which paves the way for privatisation.
The main CGT union said the 5,600 megawatts which were cut from 1100 local time on Wednesday was equivalent to 10% of available capacity.
EdF's Saint Laurent, Nogent, Chinon, Cruas and Golfech nuclear power plants were affected, according to the union.
The centre-right government wants to sell off up to 30% of EdF in order to fund urgently-needed investment in France's electricity network without putting its already overstretched finances under additional strain.
But the CGT union said the government had neglected alternatives to privatisation.